Revenue increased 79% to $394 million in the quarter, driven by growth in the number of independent OPTAVIA Coaches coupled with further improvements in coach productivity.
The number of active earning OPTAVIA Coaches reached approximately 59,200 at the end of the second quarter, a record high, that is 62% above the same quarter last year and up nearly 13% sequentially.
Revenue per active earning OPTAVIA Coach was $6,662, another new record, up nearly 14% versus last year and 3% sequentially.
A recent study of consumer health priorities and motivators commissioned by Medifast found that 93% of U.S. adults of health and wellness goals and 84% are actively working toward achieving them.
2/3 of Americans say the biggest motivator for staying consistent with health and wellness goals is feeling good mentally and physically, defined by having more energy and reducing stress and anxiety.
We achieved our $2 billion manufacturing capacity target in the second quarter, six months ahead of the original goal through the expansion of relationships with co-manufacturers.
Importantly, since we were lapping the essential start promotion from last year's second quarter, the absence of promotion provided a nice lift to gross margins, which improved by 210 basis points in the same quarter last year.
Last week, we concluded our biggest ever annual convention which was held in the new hybrid format and saw more than 15,000 global registrants.
This coach-led fundraising initiative raised over $100,000 of worthy nonprofits and advance the company's mission of providing children with education and access to resources that support healthy habits.
Revenue in the second quarter of 2021 increased 79.2% to $394.2 million from $220 million in the second quarter of 2020, reflecting continued growth in the number of active earning OPTAVIA Coaches and higher per coach productivity which resulted in more clients participating in our optimal weight five & one Plan.
We achieved another record for active earning OPTAVIA Coaches, ending the quarter with approximately 59,200 and generating sequential growth of 12.8% compared to Q1 and an increase of 62.2% from last year's second quarter.
Average revenue per active earning OPTAVIA Coach for the second quarter was $6,662, setting another record and up 3.2% from the prior high set just last quarter.
Versus a year ago, revenue per active earning of OPTAVIA Coach was up 13.9%.
Gross profit for the second quarter of 2021 increased 84.4% to $293.7 million compared to $159.3 million in the prior year period.
Gross profit as a percentage of revenue was 74.5%, up 210 basis points compared to 72.4% in the second quarter of 2020.
SG&A for the second quarter of 2021 increased 77% to $232.3 million compared to $131.2 million for the second quarter of 2020.
SG&A as a percentage of revenue decreased 70 basis points year-over-year to 58.9% versus 59.6% in the second quarter of 2020.
Income from operations increased $33.3 million to $61.4 million from $28.1 million in the prior year period, reflecting significant improvement in gross profit margin coupled with leverage of SG&A expenses.
Income from operations as a percentage of revenue was 15.6% for the quarter, an increase of 280 basis points from the year ago period.
The effective tax rate was 23.4% for the second quarter of 2021 compared to 22.1% in last year's second quarter.
Net income in the second quarter of 2021 was $47 million or $3.96 per diluted share based on approximately 11.9 million shares of common stock outstanding.
This compares to net income of $21.9 million or $1.86 per diluted share based on approximately 11.8 million shares of common stock outstanding in last year's second quarter.
Our balance sheet remains very strong with cash, cash equivalents and investment securities of $197.4 million as of June 30, 2021, compared to $174.5 million at December 31, 2020.
On the first quarter call, I provided additional detail around our capital allocation priorities and discussed that we expect higher levels of capital expenditures over the next 24 months to expand our technology and supply chain capabilities.
To that end, during the second quarter, we repurchased $12.2 million of stock, which is up from $7.5 million of repurchase activity in the first quarter, bringing our year-to-date total to $19.7 million through the first half of 2021.
Finally, in June 2021, our Board of Directors declared a quarterly cash dividend of $16.9 million or $1.42 per share, which is payable on August 6.
For the full year 2021, we expect revenue in the range of $1.425 billion to $1.525 billion and diluted earnings per share to be in the range of $12.70 to $14.17.
Our guidance also assumes a 23.25% to 24.25% effective tax rate.

Summary:
Revenue in the second quarter of 2021 increased 79.2% to $394.2 million from $220 million in the second quarter of 2020, reflecting continued growth in the number of active earning OPTAVIA Coaches and higher per coach productivity which resulted in more clients participating in our optimal weight five & one Plan.
We achieved another record for active earning OPTAVIA Coaches, ending the quarter with approximately 59,200 and generating sequential growth of 12.8% compared to Q1 and an increase of 62.2% from last year's second quarter.
Net income in the second quarter of 2021 was $47 million or $3.96 per diluted share based on approximately 11.9 million shares of common stock outstanding.
For the full year 2021, we expect revenue in the range of $1.425 billion to $1.525 billion and diluted earnings per share to be in the range of $12.70 to $14.17.