<PAGE>   1
 
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                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                            ------------------------
 
                                  FORM 10-K/A
                          AMENDMENT NO. 1 TO FORM 10-K
                            ------------------------
 
                      FOR ANNUAL AND TRANSITIONAL REPORTS
                        PURSUANT TO SECTIONS 13 OR 15(D)
                     OF THE SECURITIES EXCHANGE ACT OF 1934
 
[X]   ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 (D) OF THE SECURITIES EXCHANGE
      ACT OF 1934
 
     FOR THE FISCAL YEAR ENDED DECEMBER 31, 1998 OR
[ ]   TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (D) OF THE SECURITIES
      EXCHANGE ACT OF 1934
 
                         COMMISSION FILE NUMBER 0-21003
 
                            ------------------------
 
                              TWINLAB CORPORATION
  (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CERTIFICATE OF INCORPORATION)
 
<TABLE>
<S>                                                          <C>
                          DELAWARE                                                    11-3317986
      (STATE OR OTHER JURISDICTION OF INCORPORATION OR                 (I.R.S. EMPLOYER IDENTIFICATION NUMBER)
                        ORGANIZATION)
                     150 MOTOR PARKWAY
                    HAUPPAUGE, NEW YORK                                                 11788
          (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)                                    (ZIP CODE)
</TABLE>
 
                                 (516) 467-3140
              (REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE)
 
<TABLE>
<S>                                                          <C>
SECURITIES REGISTERED PURSUANT TO SECTION 12(B) OF THE ACT:                              NONE
 
SECURITIES REGISTERED PURSUANT TO SECTION 12(G) OF THE ACT:                 COMMON STOCK, $1.00 PAR VALUE
</TABLE>
 
     Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days.
                             Yes  [X]       No  [ ]
 
     Indicate by check mark if disclosure of delinquent filers pursuant to Item
405 of Regulation S-K is not contained herein, and will not be contained, to the
best of registrant's knowledge, in definitive proxy or information statements
incorporated by reference in part III of this Form 10-K or any amendment to this
Form 10-K.  [X]
 
     The aggregate market value of shares of Common Stock of the registrant held
by non-affiliates based on the closing sale price of the Common Stock on April
27, 1999 as reported on the Nasdaq National Market was $165,702,230.
 
     As of April 27, 1999, the registrant had 32,705,049 shares of Common Stock
outstanding.
 
                   DOCUMENTS INCORPORATED BY REFERENCE: None.
 
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<PAGE>   2
 
                              TWINLAB CORPORATION
                                  FORM 10-K/A
                                     INDEX
 
                                    PART III
 
<TABLE>
<CAPTION>
                                                              PAGE
                                                              ----
<S>                                                           <C>
Item 10.  Directors and Executive Officers of the
  Registrant................................................    3
Item 11.  Executive Compensation............................    6
Item 12.  Security Ownership of Certain Beneficial Owners
  and Management............................................   11
Item 13.  Certain Relationships and Related Transactions....   12
Signatures
</TABLE>
 
                                        2
<PAGE>   3
 
                                AMENDMENT NO. 1
                           TO THE FORM 10-K FILED BY
                     TWINLAB CORPORATION ON MARCH 31, 1999
 
     The following Items were omitted from the Form 10-K filed by Twinlab
Corporation on March 31, 1999, and such Form 10-K is hereby amended to include
Part III as hereinafter set forth.
 
                                    PART III
 
ITEM 10.  DIRECTORS AND EXECUTIVE OFFICERS OF THE REGISTRANT
 
            INFORMATION CONCERNING DIRECTORS AND EXECUTIVE OFFICERS
 
     The following table provides certain information as of March 31, 1999 about
each of the Company's directors and executive officers. Each director serves a
one year term, until his successor is duly elected and qualified. Brian
Blechman, Dean Blechman, Neil Blechman, Ross Blechman and Steve Blechman (the
"Blechman Brothers") are brothers.
 
<TABLE>
<CAPTION>
                                                                                     DIRECTOR
            NAME                AGE            POSITIONS WITH THE COMPANY             SINCE
            ----                ---            --------------------------            --------
<S>                             <C>    <C>                                           <C>
 
Ross Blechman(1)                45     Chairman of the Board, Chief Executive Of-      1996
                                       ficer, President and Director
 
Brian Blechman(2)               48     Executive Vice President, Treasurer and         1996
                                       Director
 
Dean Blechman                   41     Executive Vice President and Director           1996
 
Neil Blechman                   48     Executive Vice President, Secretary and         1996
                                       Director
 
Steve Blechman                  45     Executive Vice President and Director;          1996
                                       Chairman of the Board, Chief Executive
                                       Officer, Director and President of
                                       Advanced Research Press
 
Stephen L. Welling              44     President -- Health and Natural Food Store      1997
                                       Division and Director
 
John G. Danhakl(1)(2)           42     Director                                        1996
 
Jonathan D. Sokoloff(1)(2)      41     Director                                        1996
 
John McCusker                   59     Chief Financial Officer
</TABLE>
 
---------------
(1) Member of the Compensation Committee.
(2) Member of the Audit Committee.
 
     The business experience, principal occupation, employment and certain other
information concerning each director and executive officer is set forth below.
 
     Ross Blechman became Chairman of the Board, Chief Executive Officer,
President and Director of the Company on May 7, 1996. Mr. Blechman joined Twin
Laboratories, Inc. in 1974 and served as Vice President, Operations of the
Company prior to May 7, 1996. Mr. Blechman is Chairman of the Board, President,
Chief Executive Officer and Director of Twin, an Executive Vice President and
Director of Advanced Research Press, Inc. ("ARP") and a Vice President and
Director of Changes International.
 
                                        3
<PAGE>   4
 
     Brian Blechman became an Executive Vice President, Treasurer and Director
of the Company on May 7, 1996. Mr. Blechman joined Twin Laboratories, Inc. in
1972 and served as Vice President, Purchasing & Quality Control of the Company
prior to May 7, 1996. He is responsible for purchasing, plant operations,
quality control and management. Mr. Blechman is an Executive Vice President and
Director of Twin and ARP, and a Vice President, Treasurer and a Director of
Changes International.
 
     Dean Blechman became an Executive Vice President and Director of the
Company on May 7, 1996. Mr. Blechman joined Twin Laboratories, Inc. in 1979 and
served as Vice President, Sales of the Company prior to May 7, 1996. He is
responsible for sales and distribution. Mr. Blechman is an Executive Vice
President and Director of Twin and ARP and a Vice President and Director of
Changes International.
 
     Neil Blechman became an Executive Vice President, Secretary and Director of
the Company on May 7, 1996. Mr. Blechman joined Twin Laboratories, Inc. in 1972
and served as Vice President, Marketing & Advertising of the Company prior to
May 7, 1996. He is responsible for marketing and advertising activities,
promotional programs, merchandising strategies, packaging, trade shows and
public relations. Mr. Blechman is an Executive Vice President and Director of
Twin and ARP and a Vice President, Secretary and a Director of Changes
International.
 
     Steve Blechman became an Executive Vice President and Director of the
Company and Chairman of the Board, Chief Executive Officer, Director and
President of ARP on May 7, 1996. Mr. Blechman joined Twin Laboratories, Inc. in
1974 and served as Vice President, Product Development & Marketing of the
Company prior to May 7, 1996. He is involved in marketing, product development,
customer service, public relations and the operations of ARP. Mr. Blechman is an
Executive Vice President and Director of Twin and a Vice President and Director
of Changes International.
 
     Stephen L. Welling was elected to the Board of Directors of the Company on
September 16, 1997 and became President-Health and Natural Food Store Division
on March 3, 1999. Mr. Welling previously was the President of Nature's Herbs
Division of Twin since May 7, 1996. Mr. Welling joined Natur-Pharma Inc. in 1977
as the controller and served as President of Natur-Pharma Inc. prior to May 7,
1996. Prior to his promotion to President, Mr. Welling served as Vice President
of Operations of Natur-Pharma Inc. with responsibility for manufacturing,
personnel, quality management, legal affairs and finance. Mr. Welling is on the
board of directors of the National Nutritional Foods Association, a leading
trade organization of the industry's retailers, distributors, suppliers and
manufacturers.
 
     John G. Danhakl became a director of the Company on May 7, 1996. He has
been an executive officer and an equity owner of Leonard Green & Partners, L.P.
("LGP"), a merchant banking firm which manages Green Equity Investors II, L.P.
("GEI"), since 1995. Mr. Danhakl had previously been a Managing Director at
Donaldson, Lufkin & Jenrette Securities Corporation ("DLJ") and had been with
DLJ since 1990. Prior to joining DLJ, Mr. Danhakl was a Vice President at Drexel
Burnham Lambert Incorporated ("Drexel"). Mr. Danhakl is also a director of Big 5
Corp., Communications & Power Industries, Inc., Leslie's Poolmart, Inc.,
Hechinger Company, The Arden Group, Inc. and Liberty Group Publishing. Mr.
Danhakl also serves as a director of Twin and ARP.
 
     Jonathan D. Sokoloff became a director of the Company on May 7, 1996. He
has been a partner of LGA since 1990 and has been an executive officer and
equity owner of LGP since its formation in 1994. Mr. Sokoloff had previously
been a Managing Director at Drexel. Mr. Sokoloff is a director of Carr-Gottstein
Foods Co., Gart Sports Company and Hechinger Company. Mr. Sokoloff also serves
as a Director of Twin and ARP.
 
     John McCusker became the Chief Financial Officer of the Company on November
3, 1997. He is responsible for financial management and the Company's Management
Information Systems department. He was previously an independent financial
consultant. From 1987 to 1996, Mr. McCusker was Chief Financial Officer for
Geraghty & Miller, Inc. Upon its 1995 merger with Arcadis NV, he was appointed
to the additional position of Senior Vice President.
 
                                        4
<PAGE>   5
 
COMMITTEES AND MEETINGS OF THE BOARD OF DIRECTORS
 
     The Board of Directors of the Company has an Audit Committee and a
Compensation Committee. In 1998, the Board of Directors met three times and
acted by unanimous written consent on two occasions, the Compensation Committee
met once and the Audit Committee met once.
 
     The Audit Committee reviews the adequacy of internal controls, the results
and scope of annual audits and other services provided by the Company's
independent auditors. In 1998, the Audit Committee was comprised of Brian
Blechman, John Danhakl and Jennifer Holden Dunbar (until Ms. Holden Dunbar's
resignation in July 1998 as a director of the Company and as a member of the
Audit Committee). Jonathan Sokoloff became a member of the Audit Committee on
February 25, 1999.
 
     The Compensation Committee establishes salaries, bonuses and other forms of
compensation for executives of the Company and such other employees of the
Company as assigned thereto by the Board. In 1998, the Compensation Committee
was comprised of Ross Blechman, John Danhakl, Jennifer Holden Dunbar (until Ms.
Holden Dunbar's resignation in July 1998 as a director of the Company and as a
member of the Compensation Committee) and Jonathan Sokoloff.
 
     The Company does not have a nominating committee. The functions customarily
performed by a nominating committee are performed by the Board of Directors as a
whole. Any stockholder who wishes to make a nomination at an annual or special
meeting for the election of directors must do so in compliance with the
applicable procedures set forth in the Company's By-laws. The Company will
furnish copies of such By-law provisions upon written request to the General
Counsel's Office at the Company's principal executive offices, 150 Motor
Parkway, Hauppauge, New York 11788.
 
     During the period in which each person served as a director, each director
attended at least 75% of the aggregate number of meetings of the Board of
Directors and the committees of the Board on which such person served.
 
COMPLIANCE WITH SECTION 16(A) OF THE SECURITIES EXCHANGE ACT OF 1934
 
     Section 16(a) of the Securities Exchange Act of 1934, as amended, requires
the Company's directors and executive officers and persons who beneficially own
more than ten percent of the Company's Common Stock to report their ownership of
and transactions in the Company's Common Stock to the Securities and Exchange
Commission and The Nasdaq National Stock Market. Copies of these reports are
also required to be supplied to the Company. The Company believes, based solely
on a review of the copies of such reports received by the Company, that all
applicable Section 16(a) reporting requirements were complied with during 1998.
 
                                        5
<PAGE>   6
 
ITEM 11.  EXECUTIVE COMPENSATION
 
     Summary Compensation Table.  The following table sets forth compensation
earned, whether paid or deferred, by the Company's Chief Executive Officer and
its other four most highly compensated executive officers (collectively, the
"Named Executive Officers") for services rendered in all capacities to the
Company during the years ended December 31, 1996, 1997 and 1998. Prior to May 7,
1996, the Blechman Brothers collectively acted in a similar capacity to a Chief
Executive Officer.
 
<TABLE>
<CAPTION>
                                                                  ANNUAL COMPENSATION
                                   ----------------------------------------------------------------------------------
                                                                               ALL OTHER ANNUAL        ALL OTHER
NAME AND PRINCIPAL OCCUPATION      YEAR      SALARY($)        BONUS($)(A)     COMPENSATION($)(B)   COMPENSATION($)(C)
-----------------------------      ----      ---------        -----------     ------------------   ------------------
<S>                                <C>    <C>               <C>               <C>                  <C>
Ross Blechman
    Chairman of the Board,
    President and Chief
    Executive Officer............  1998   $      428,305    $     300,200       $      31,462         $     1,365
                                   1997          412,869          224,680              32,693               1,365
                                   1996          403,077          324,950              18,650               1,365
 
Brian Blechman
    Executive Vice President
    and Treasurer................  1998          428,305          300,200              22,275               1,660
                                   1997          412,869          224,680              24,102               1,660
                                   1996          403,077          324,950              19,607               1,660
 
Dean Blechman
    Executive Vice President.....  1998          428,305          300,200              23,162               1,073
                                   1997          412,869          224,680              23,746               1,073
                                   1996          403,077          324,950              26,531               1,073
 
Neil Blechman
    Executive Vice President
    and Secretary................  1998          428,305          300,200              25,709               1,660
                                   1997          412,869          224,680              28,520               1,660
                                   1996          403,077          324,950              23,294               1,660
 
Steve Blechman
    Executive Vice President.....  1998          428,305          300,200              22,714               1,365
                                   1997          412,869          224,680              25,784               1,365
                                   1996          403,077          324,950              28,653               1,365
</TABLE>
 
---------------
 
(a) A description of the Company's bonus arrangements is contained below under
    "-- Employment Agreements."
 
(b) For fiscal year 1996, includes (i) payment of premiums for executive medical
    insurance policies; (ii) matching contributions under Twin's 401(k) plan;
    (iii) automobile allowances; and (iv) payment of premiums for TLI's
    cafeteria benefits program and Twin's successor cafeteria benefits program,
    for each of the Blechman Brothers. For fiscal years 1997 and 1998, includes
    (i) payment of premiums for executive medical insurance policies; (ii)
    matching contributions under Twin's 401(k) plan; (iii) automobile
    allowances; and (iv) payment of premiums for Twin's cafeteria benefits
    program and Twin's successor cafeteria benefits program, for each of the
    Blechman Brothers.
 
(c) For fiscal years 1996, 1997 and 1998, represents the payment of premiums for
    term life insurance policies for each of the Blechman Brothers.
 
DIRECTOR COMPENSATION
 
     Directors who are employees of the Company receive no compensation for
serving on the Board of Directors. Non-employee directors are reimbursed for
their out-of-pocket expenses in attending Board meetings. See "Certain
Relationships and Related Transactions -- Transactions with LGP" for a
description of the Management Services Agreement between LGP, the Company and
Twin.
 
                                        6
<PAGE>   7
 
EMPLOYMENT AGREEMENTS
 
     On May 7, 1996, Twin entered into employment agreements with each of the
Blechman Brothers (each an "Employment Agreement"). Pursuant to the terms of the
Employment Agreement, the relevant individual will be employed as an executive
of the Company, Twin and ARP until November 15, 1999, renewable for terms of one
year thereafter. The Employment Agreement provides for a base salary of $400,000
(as adjusted annually for inflation), in addition to other customary perquisites
and benefits. In addition to receiving a base salary, the executive is also
eligible to participate in Twin's Bonus Plan, which entitles such individual to
a bonus payment of up to 128% of his base salary for the relevant calendar year
based on annual increases in EBITDA (as defined therein) realized by the Company
for each year of the employment term. The Employment Agreement also provides,
subject to certain exceptions, that upon a termination of the individual's
employment during the term thereof (other than for "cause" as defined therein),
Twin is generally obligated to pay the individual an amount equal to his base
salary for the remaining term under the Employment Agreement (which, for this
purpose, will be a three year period).
 
     On May 7, 1996, Twin entered into an employment agreement with Stephen
Welling to serve as President of Nature's Herbs Division of Twin (the
"Division") (as amended, the "Welling Employment Agreement"). The Welling
Employment Agreement provides that Mr. Welling will be employed as an executive
of the Company for a term of three years, renewable for terms of one year
thereafter. The Welling Employment Agreement provides for a base salary of
$200,000 (as adjusted annually for inflation), in addition to other customary
perquisites and benefits. In addition to receiving a base salary, Mr. Welling is
also eligible to participate in the Division Bonus Plan, which entitles him to a
bonus payment of up to 202.5% of his base salary for the relevant calendar year
based on annual increases in EBITDA (as defined therein) realized by the
Division for each year of the employment term. The Welling Employment Agreement
also provides, subject to certain exceptions, that upon a termination of Mr.
Welling's employment during the term thereof (other than for "cause" as defined
therein), Twin is generally obligated to pay Mr. Welling an amount equal to his
base salary for the remaining term under the Welling Employment Agreement.
 
     On May 7, 1996, Twin entered into consulting agreements with each of David
and Jean Blechman, the parents of the Blechman Brothers and the founders of TLI
(together, the "Consultants") (each a "Consulting Agreement"). The Consulting
Agreement provides that the relevant individual be engaged as an independent
consultant to the Company, Twin and ARP for a term of five years. As
consideration for such consulting services, Twin is obligated to pay the
individual an annual consulting fee of $100,000, in addition to certain limited
perquisites and benefits.
 
     In May 1996, the Company and Twin entered into non-competition agreements
with each of the Blechman Brothers and Stephen Welling (collectively, the
"Senior Executive Officers") and the Consultants (each a "Non-Competition
Agreement"). The term of the Non-Competition Agreement of each of the Blechman
Brothers and of each of the Consultants and Stephen Welling is five years and
three years, respectively. The Non-Competition Agreement generally prevents the
individual from participating in any manner in the management, operation and/or
ownership of any entity which is engaged in similar lines of business to those
of the Company.
 
COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION
 
     In 1998, the Company's Compensation Committee consisted of Ross Blechman,
John Danhakl, Jennifer Holden Dunbar (until Ms. Holden Dunbar's resignation in
July 1998 as a director of the Company and as a member of the Compensation
Committee) and Jonathan Sokoloff. In addition to being a director and executive
officer of the Company, Mr. Blechman is also Chairman of the Board, President,
Chief Executive Officer and Director of Twin and an Executive Vice President and
Director of ARP. Messrs. Sokoloff and Danhakl are also directors of Twin and
ARP. Ms. Holden Dunbar was a director of Twin and ARP until her resignation in
July 1998. See "Certain Relationships and Related Transactions" for a
description of certain transactions involving the Company and the members of the
Compensation Committee or entities controlled by such individuals.
 
                                        7
<PAGE>   8
 
REPORT OF THE COMPENSATION COMMITTEE OF THE BOARD OF DIRECTORS ON EXECUTIVE
COMPENSATION
 
     The Compensation Committee, reviews and approves the compensation of
executives of the Company and such other employees of the Company as assigned
thereto by the Board and makes recommendations to the Board with respect to
standards for setting compensation levels. In 1998, the Company's Compensation
Committee consisted of Ross Blechman, John Danhakl, Jennifer Holden Dunbar
(until Ms. Holden Dunbar's resignation in July 1998 as a director of the Company
and as a member of the Compensation Committee) and Jonathan Sokoloff. The
Compensation Committee adopted the Report on Executive Compensation set forth
below.
 
     The Company does not presently have a stock option committee. The functions
customarily performed by a stock option committee are performed by the Board of
Directors as a whole.
 
REPORT ON EXECUTIVE COMPENSATION
 
     The Company's executive compensation for fiscal 1998 consisted of two
primary components: base salary and bonus. The level of each executive officer's
base salary and bonus is established in such officer's employment agreement,
which agreements were entered into in May, 1996. See " -- Employment
Agreements."
 
     The salary and bonus components of the Company's executive compensation are
together designed to facilitate fulfillment of the following compensation
objectives: (i) retaining competent management; (ii) rewarding management for
the attainment of short and long term accomplishments; (iii) aligning the
interests of management with those of the Company's stockholders; and (iv)
relating executive compensation to the achievement of Company goals and the
Company's financial performance.
 
     Base Salary.  The base salary of each of the Senior Executive Officers in
fiscal 1998 was paid in accordance with the terms of their respective employment
agreements. Such base salary is subject to annual adjustment for inflation.
 
     Bonuses.  The Compensation Committee believes that the awarding of annual
bonuses provides an incentive and reward for short-term financial success and
long-term Company growth. The bonus component of the long-term employment
agreements of each of the Senior Executive Officers is intended to link
compensation in significant part to the Company's financial performance and the
attainment of Company goals. The bonus earned by each of the Senior Executive
Officers was calculated in accordance with a formula set forth in the relevant
officer's employment agreement and entitles such individual to a bonus
calculated as a percentage of base salary based on annual increases in EBITDA
realized by Twin or the Division, as applicable, for each fiscal year. See
" -- Employment Agreements."
 
     Stock Incentive Plans.  The Twinlab Corporation 1996 Stock Incentive Plan
(the "1996 Plan") provides for the issuance of a total of up to 400,000
authorized and unissued shares of Common Stock as awards in the form of (i)
incentive stock options, (ii) nonqualified stock options, (iii) stock
appreciation rights, (iv) restricted stock and (v) performance shares. No
individuals who are directors of the Company (including the Blechman Brothers)
are eligible to receive awards under the 1996 Plan. Prior to the consummation of
the Company's initial public offering in 1996 (the "IPO"), Stephen L. Welling
was awarded 8,000 nonqualified stock options under the 1996 Plan, such options
having an exercise price equal to $12.00, the IPO price. In 1998, certain
employees of the Company were awarded an aggregate of 214,000 nonqualified stock
options with exercise prices of $29.375 per share. Such options become
exercisable over five years from the date of grant at the rate of 20% of the
grant each year.
 
     The Twinlab Corporation 1998 Stock Incentive Plan provides for the issuance
of a total of up to 1,000,000 authorized and unissued shares of Common Stock in
the form of: (i) incentive stock options, (ii) non-qualified stock options,
(iii) stock appreciation rights, (iv) restricted stock, (v) restricted stock
units, (vi) dividend equivalent rights and (vii) other stock based awards.
Awards may be made to such officers and other employees of the Company and its
subsidiaries (including employees who are directors and prospective employees
who become employees), and to such consultants to the Company and its
subsidiaries as the Compensation Committee shall in its discretion select. In
1998, an employee of the Company was awarded a
                                        8
<PAGE>   9
 
nonqualified stock option to purchase 50,000 shares of Common Stock at an
exercise price of $25.00 per share. Such option becomes exercisable over five
years from the date of grant at the rate of 20% of the grant each year.
 
     Profit Sharing Plan. Prior to July 1, 1996, Twin sponsored an employee
profit sharing and savings plan (the "Twin Plan") and Natur-Pharma Inc.
sponsored an Employee Savings and Investment Plan (the "NP Plan"), which covered
all of Twin's and Natur-Pharma Inc.'s eligible employees, respectively.
Executive officers of Twin and Natur-Pharma Inc. participated in the Twin Plan
and NP Plan, respectively, on the same terms as other employees. Effective July
1, 1996, the Twin Plan was amended and restated and merged with the NP Plan to
form the Twin Laboratories Inc. 401(k) Plan (the "401(k) Plan"). Eligible
employees, including executive officers of the Company and Twin, may contribute
up to 15% of their annual compensation to the 401(k) Plan, subject to certain
limitations, and Twin will match 50% of such contributions.
 
     Compensation of the Chief Executive Officer. The compensation package of
Mr. Ross Blechman, the Company's President and Chief Executive Officer, like
that of the other Senior Executive Officers, primarily consists of base salary
and bonus components. The levels of base salary and bonus, as well as the
factors considered in determining such levels, are established by Mr. Blechman's
Employment Agreement and are identical to those of the other Blechman Brothers.
In 1998, Ross Blechman earned a base salary of $428,305 and a bonus of $300,200.
In addition, pursuant to his employment agreement, Mr. Blechman receives certain
other customary perquisites and benefits. As of April 27, 1999, Ross Blechman
beneficially owned 1,660,497 shares, or 5.1%, of the Company's Common Stock. See
" -- Security Ownership of Certain Beneficial Owners and Management."
 
                                          Ross Blechman
                                          John G. Danhakl
                                          Jonathan D. Sokoloff
 
                                        9
<PAGE>   10
 
                            STOCK PERFORMANCE GRAPH
 
     The following graph depicts the cumulative total return on the Company's
Common Stock compared to the cumulative total return for the Nasdaq
Composite -- U.S. and the Nasdaq Health Index. The graph assumes an investment
of $100 on November 15, 1996, when the Company's stock was first traded in a
public market. Reinvestment of dividends is assumed in all cases.
 
<TABLE>
<CAPTION>
                                                   TWINLAB CORPORATION         NASDAQ HEALTH INDEX       NASDAQ COMPOSITE - U.S.
                                                   -------------------         -------------------       -----------------------
<S>                                             <C>                         <C>                         <C>
'Nov 15 96'                                              100.00                      100.00                      100.00
'Dec 96'                                                 101.06                      102.79                      102.32
'Mar 97'                                                 112.50                       95.97                       90.97
'Jun 97'                                                 200.00                      107.12                      114.74
'Sept 97'                                                170.63                      110.55                      134.48
'Dec 97'                                                 206.25                      104.75                      125.84
'Mar 98'                                                 337.50                      114.89                      146.97
'Jun 98'                                                 364.06                      104.27                      150.98
'Sept 98'                                                213.54                       78.36                      136.38
'Dec 98'                                                 109.38                       88.75                      176.96
</TABLE>
 
     The comparisons in the table and on the graph above are required by the
Securities and Exchange Commission and are not intended to forecast or be
indicative of possible future performance of the Company's Common Stock.
 
                                       10
<PAGE>   11
 
ITEM 12.  SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT
 
     The following table sets forth information, as of April 27, 1999,
concerning the Common Stock of the Company beneficially owned (i) by each
director of the Company, (ii) by the Named Executive Officers and all executive
officers and directors as a group, and (iii) by each stockholder known by the
Company to be the beneficial owner of more than 5% of the outstanding Common
Stock. Unless otherwise indicated in the footnotes to the table, the beneficial
owners named have, to the knowledge of the Company, sole voting and dispositive
power with respect to the shares beneficially owned, subject to community
property laws where applicable.
 
<TABLE>
<CAPTION>
                                                                             PERCENT OF
                                                              NUMBER OF        SHARES
            NAME AND ADDRESS OF BENEFICIAL OWNER              SHARES(A)    OUTSTANDING (A)
            ------------------------------------              ---------    ---------------
<S>                                                           <C>          <C>
Green Equity Investors II, L.P.
  c/o Leonard Green & Partners, L.P.
  11111 Santa Monica Boulevard, Suite 2000
  Los Angeles, CA 90025.....................................   4,879,999        14.9
John G. Danhakl (b)
  c/o Leonard Green & Partners, L.P.
  11111 Santa Monica Boulevard, Suite 2000
  Los Angeles, CA 90025.....................................   4,879,999        14.9
Jonathan D. Sokoloff (b)
  c/o Leonard Green & Partners, L.P.
  11111 Santa Monica Boulevard, Suite 2000
  Los Angeles, CA 90025.....................................   4,879,999        14.9
Brian Blechman
  c/o Twin Laboratories Inc.
  150 Motor Parkway
  Hauppauge, NY 11788.......................................   1,659,246         5.1
Dean Blechman (c)
  c/o Twin Laboratories Inc.
  150 Motor Parkway
  Hauppauge, NY 11788.......................................   1,660,080         5.1
Neil Blechman (d)
  c/o Twin Laboratories Inc.
  150 Motor Parkway
  Hauppauge, NY 11788.......................................   1,660,497         5.1
Ross Blechman (d)
  c/o Twin Laboratories Inc.
  150 Motor Parkway
  Hauppauge, NY 11788.......................................   1,660,497         5.1
Steve Blechman (c)
  c/o Twin Laboratories Inc.
  150 Motor Parkway
  Hauppauge, NY 11788.......................................   1,660,080         5.1
John McCusker (e)
  c/o Twin Laboratories
  150 Motor Parkway
  Hauppauge, NY 11788.......................................      11,500       *
Stephen Welling (f)
  c/o Twin Laboratories Inc.
  150 Motor Parkway
  Hauppauge, NY 11788.......................................      31,970       *
All executive officers and directors as a group (9
  persons)(g)...............................................  13,223,869        40.4
</TABLE>
 
                                       11
<PAGE>   12
 
---------------
(a) Does not include an aggregate of 323,000 shares of Common Stock issuable
    upon exercise of outstanding stock options with a weighted average price of
    $23.02 per share.
 
(b) The shares shown as beneficially owned by Messrs. Danhakl and Sokoloff
    represent 4,879,999 shares owned of record by GEI. GEI is a Delaware limited
    partnership managed by LGP, which is an affiliate of the general partner of
    GEI. Each of Leonard I. Green, Jonathan D. Sokoloff, John G. Danhakl, Peter
    J. Nolan and Gregory J. Annick, either directly (whether through ownership
    interest or position) or through one or more intermediaries, may be deemed
    to control LGP and such general partner. LGP and such general partner may be
    deemed to control the voting and disposition of the shares of Common Stock
    of TLC owned by GEI. As such, Messrs. Sokoloff and Danhakl may be deemed to
    have shared voting and investment power with respect to all shares held by
    GEI. However, such individuals disclaim beneficial ownership of the shares
    held by GEI.
 
(c) The shares shown as beneficially owned by each of Dean Blechman and Steve
    Blechman each include 834 shares of Common Stock beneficially owned by their
    respective minor children. Dean Blechman and Steve Blechman disclaim
    beneficial ownership of such shares.
 
(d) The shares shown as beneficially owned by each of Ross Blechman and Neil
    Blechman each include 1,251 shares of Common Stock owned by their respective
    minor children. Ross Blechman and Neil Blechman disclaim beneficial
    ownership of such shares.
 
(e) The shares shown as beneficially owned by Mr. McCusker include 10,000 shares
    subject to options exercisable within 60 days, but do not include 500 shares
    of Common Stock owned by Mr. McCusker's spouse, Brenda McCusker. Mr.
    McCusker disclaims beneficial ownership of such shares.
 
(f) The shares shown as beneficially owned by Mr. Welling include 3,200 shares
    subject to options exercisable within 60 days.
 
(g) Includes the shares referred to in Notes (b), (c), (d), (e) and (f) above.
 
  * Less than 1%.
 
ITEM 13.  CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS
 
EMPLOYMENT AGREEMENTS
 
     The Company has employment agreements with each of the Senior Executive
Officers.
 
TRANSACTIONS WITH LGP
 
     LGP is the investment advisor to and an affiliate of the general partner of
GEI, which owns 14.9% of the outstanding shares of Common Stock of the Company.
Messrs. Danhakl and Sokoloff, stockholders and directors of the general partner
of LGP, are directors of the Company and Twin. Ms. Holden Dunbar, a stockholder
and general partner of LGP, was a director of the Company and Twin until her
resignation in July 1998.
 
     The Company and Twin were parties to a Management Services Agreement with
LGP pursuant to which LGP received an annual retainer fee of $400,000 plus
reasonable expenses for providing certain management, consulting and financial
planning services (the "LGP Management Fee"). The Company believes that the
contacts and expertise provided by LGP in these areas enhanced the Company's
opportunities and management's expertise in these matters and that the fees paid
to LGP fairly reflect the value of the services provided by LGP. In 1998, the
specialized consulting services provided by LGP overlapped to some extent with
the role of Messrs. Danhakl and Sokoloff and Ms. Holden Dunbar as directors of
the Company and Twin, for which they did not receive any additional
compensation. See "Executive Compensation -- Director Compensation." The
Management Services Agreement terminated in April 1998. Ms. Holden Dunbar
resigned as a director of the Company in July 1998.
 
                                       12
<PAGE>   13
 
                                   SIGNATURES
 
     Pursuant to the requirements of Section 13 or 15(d) of the Securities and
Exchange Act of 1934, the Registrant has duly caused this Form 10-K/A Amendment
No. 1 to Form 10-K to be signed on its behalf by the undersigned, thereunto duly
authorized.
                                          TWINLAB CORPORATION
 
                                          By:       /s/ ROSS BLECHMAN
                                            ------------------------------------
                                                       Ross Blechman
                                             Chairman, Chief Executive Officer
                                                        and President
Date:  April 30, 1999