Obesity

ReportHigh Fat Diets for Diet-Induced Obesity Models

Matched Formulas
When planning a diet-induced obesity study, the composition of thehigh-fat diet deserves attention. All too often in the literature, onewill find that diets used in the experiments are not well matched,
thereby introducing confounding factors. For example, in many casesa chow (cereal based diet) is used as a low-fat “control” diet for apurified high-fat diet. Chows diets contain plant-derived ingredients
which are subject to changes in the growing season and will vary incomposition at the time of harvest. Thus, diet formulas may change
based on the nutritional composition. Purified ingredients, on theother hand, are highly refined and contain just a single nutrient (ie.
sucrose = carbohydrate). These ingredients have little variability andtherefore provide consistency between batches. There are numerous
differences between chows and purified diets, creating countless
variables, thus making it difficult to interpret the results when thesediets are used together in a study (3). In addition, chows containplant-based compounds such as phytoestrogens which have beenshown to reduce the degree of weight gain (4). For these reasons, alow-fat purified diet containing the same ingredients with a closelymatched composition to the high-fat formula should be used as acontrol diet.

Cafeteria Diets
In the early days of rodent diet-induced obesity research, somescientists used what is known as the cafeteria diet. In this model, theanimal self-selects from highly palatable, readily available foods
including cookies, candy, cheese, and processed meats. These foods
contain a substantial amount of salt, sugar, and fat and are meant tosimulate the human Western diet. However, the nutritive and nonnutritive components of these foods are not well defined. In addition,
the animal may choose a different selection of foods each day.
Therefore, these diets cannot be accurately replicated for futurestudies, which makes this type of diet a poor choice for scientificresearch (5).

Revise1000

Body Weight (g)A Brief Review of the Scientific Literature- October 2008
by Angela M. Gajda, M.S., Senior Scientist, Research Diets, Inc.

Genetic and environmental factors play a role in the developmentof obesity, and diet is one of the main environmental factors that
contributes to this disease. Human studies have shown that
increased fat intake is associated with body weight gain which canlead to obesity and other related metabolic diseases. Animal rodent
models are therefore useful tools for studying obesity as they willreadily gain weight when fed high-fat diets (1, 2).

Repeat750

500250

DRDIO

047

1013

16

19222528

Age (weeks)
FIGURE 1. Growth rate of DIO (n = 12) and DR (n = 12) rats fed D12451 HFD(45 kcal% fat) diet used in meal analysis. Values are means ± SEM. Body weights are
significantly different at all time points (p < 0.05). Graphic representation - for details
see reference (16).

Calories from Fat
High-fat diets used in laboratory research typically contain about 32
to 60% of calories from fat. From a nutritional perspective, a humandiet of 60 kcal% fat would be considered extreme. That said, dietswith 60 kcal% fat are commonly used to induce obesity in rodents
since animals tend to gain more weight more quickly (6, 7) thereby
allowing researchers to screen their compounds after a shorter periodof time. It should also be noted that when studying the effects of adrug, nutraceutical, or gene mutation on obesity, it may be moredifficult to prevent or reverse the effects of a very high-fat diet, when
it might be possible with a diet containing a lower percentage of fat.

Type of Fat
The type of fat should be considered when choosing a high-fat dietfor an animal study. Many high-fat diets used in laboratory animal
research contain more saturated fat such as lard, beef tallow, or
coconut oil and these diets are quite capable of inducing obesity insusceptible strains. In contrast, omega-3 fatty acids have beenstudied for their health benefits. For example, it has been shownthat of animals fed similar amounts of fat, those fed diets containing
fish oil did not gain as much weight as those fed diets with moresaturated fat (8, 9) and were more insulin sensitive (10). Since fatty
acids can affect phenotype through a variety of mechanisms (geneexpression, eiconsanoid production, membrane receptor function),
it is important to include information about the type and level of fat
used in a study in order to allow other researchers to compare data.

Obesity
Animal Models

References

While most rodents tend to become obese on high-fat diets, there canbe variable responses in weight gain, glucose tolerance, insulin
resistance, triglycerides and other parameters depending on the strain.
Some inbred strains are more susceptible to obesity when fed high-fat
diets such as the C57Bl6 or AKR mouse (11). However, strains thatexhibit similar levels of weight gain may show different responses toother parameters. For example, when fed a 58 kcal% fat diet, C57Bl6
mice and AKR mice will have similar degrees of weight gain, but
C57Bl6 mice are more glucose intolerant compared to AKR mice(11). Other strains are simply more resistant to obesity, such as theSWR/J and A/J mice (12, 13). Even within the same strain, different
phenotypical responses to high fat diets have been observed between
animals bred in different facilities (14).
Rat models including
outbred SpragueDawley and Wistar
rats are popular strainsto study obesity as
they readily gain
weight on high-fat
diets. In particular,
Sprague-Dawley rats
have been studied fortheir ability to show aa variable response to ahigh-fat diet (32 or 45kcal% fat).
Some animals rapidly gain weight while others gain only as muchweight as those fed a low-fat diet (15, 16), allowing for the study ofanimals that are prone and resistant to obesity. These animals havebeen selectively bred over time to study the genetic traits of animals
with the obese or lean phenotype. Another strain, the F344xBrown
Norway rat, has been used as a model for age-related onset of obesity
since the animals gain weight until about 30 months of age (17).
When this strain was fed a diet containing 60 kcal% fat, 3 month oldrats separated into resistant and obese groups. This was in contrast to
24-month-old animals which had similar levels of weight gain anddid not require separation (18).
There has been a growing body of literature using rodents as models
of human obesity, even though there are many confounding factors
including species, strain, age of the animals, type of diet, level of fat,and type of control diet. Fortunately, there is a growing discussion
about these issues which will help scientists design studies with tightly
controlled conditions and therefore improve our understanding ofobesity and related diseases.

Where NutriPhenomics® Begins

1. Buettner R., Scholmerich J. and Bollheimer L.C. High-fat diets: modeling themetabolic disorders of human obesity in rodents.
Obesity (Silver Spring) 15: 798-808, 2007.
2. Van Heek M, Compton D.S., France CF, Tedesco RP, Fawzi AB, Graziano MP,Sybertz EJ, Strader CD and Davis HR, Jr. Diet-induced obese mice develop
peripheral, but not central, resistance to leptin. J Clin Invest 99: 385-390, 1997.
3. Warden C.H. and Fisler J.S. Comparisons of diets used in animal models ofhigh-fat feeding. Cell Metab 7: 277, 2008.
4. Cederroth C.R., Vinciguerra M., Kuhne F., Madani R., Doerge D.R., Visser T.J.,
Foti M., Rohner-Jeanrenaud F., Vassalli J.D. and Nef S. A phytoestrogen-rich dietincreases energy expenditure and decreases adiposity in mice.
Environ Health Perspect 115: 1467-1473, 2007.
5. Moore BJ. The cafeteria diet--an inappropriate tool for studies of thermogenesis.
J Nutr 117: 227-231, 1987.
6. Ghibaudi L, Cook J, Farley C, van Heek M and Hwa JJ. Fat intake affects adiposity,comorbidity factors, and energy metabolism of sprague-dawley rats.
Obes Res 10: 956-963, 2002.
7. Johnston S.L., Souter D.M., Tolkamp B.J., Gordon I.J., Illius A.W., Kyriazakis I.
and Speakman J.R. Intake compensates for resting metabolic rate variation in female
C57BL/6J mice fed high-fat diets. Obesity (Silver Spring) 15: 600-606, 2007.
8. Ikemoto S, Takahashi M, Tsunoda N, Maruyama K, Itakura H and Ezaki O.
High-fat diet-induced hyperglycemia and obesity in mice: differential effects ofdietary oils. Metabolism 45: 1539-1546, 1996.
9. Wang H, Storlien LH and Huang XF. Effects of dietary fat types on body fatness,leptin, and ARC leptin receptor, NPY, and AgRP mRNA expression. Am J Physiol
Endocrinol Metab 282: E1352-E1359, 2002.
10. Buettner R, Parhofer KG, Woenckhaus M, Wrede CE, Kunz-Schughart LA,Scholmerich J and Bollheimer LC. Defining high-fat-diet rat models: metabolic andmolecular effects of different fat types. J Mol Endocrinol 36: 485-501, 2006.
11. Rossmeisl M, Rim JS, Koza RA and Kozak LP. Variation in type 2 diabetes--related
traits in mouse strains susceptible to diet-induced obesity.
Diabetes 52: 1958-1966, 2003.
12. Surwit RS, Feinglos MN, Rodin J, Sutherland A, Petro AE, Opara EC, Kuhn CM
and Rebuffe-Scrive M. Differential effects of fat and sucrose on the development ofobesity and diabetes in C57BL/6J and A/J mice. Metabolism 44: 645-651, 1995.
13. Prpic V, Watson PM, Frampton IC, Sabol MA, Jezek GE and Gettys TW.
Adaptive changes in adipocyte gene expression differ in AKR/J and SWR/J mice
during diet-induced obesity. J Nutr 132: 3325-3332, 2002.
14. Pecoraro N., Ginsberg A.B., Warne J.P., Gomez F., la Fleur S.E. and Dallman M.F.
Diverse basal and stress-related phenotypes of Sprague Dawley rats from threevendors. Physiol Behav 89: 598-610, 2006.
15. Levin BE, Dunn-Meynell AA, Balkan B and Keesey RE. Selective breeding for
diet-induced obesity and resistance in Sprague-Dawley rats.
Am J Physiol 273: R725-R730, 1997.
16. Farley C, Cook JA, Spar BD, Austin TM and Kowalski TJ. Meal pattern analysis of
diet-induced obesity in susceptible and resistant rats. Obes Res 11: 845-851, 2003.
17. Scarpace P.J., Matheny M., Moore R.L. and Tumer N. Impaired leptin responsivenessin aged rats. Diabetes 49: 431-435, 2000.
18. Judge MK, Zhang J, Tumer N, Carter C, Daniels MJ and Scarpace PJ. Prolonged
hyperphagia with high-fat feeding contributes to exacerbated weight gain in rats
with adult-onset obesity.
Am J Physiol Regul Integr Comp Physiol 295: R773-R780, 2008.

Research Diets, Inc.
20 Jules Lane
New Brunswick, NJ 08901 USA
Tel: 732.247.2390
Fax: 732.247.2340
info@researchdiets.com© 2009 Research Diets, Inc. All rights reserved. Obesity-3000-2-09

Obesity
The “Original” High-Fat Diets
Research Diets, Inc. formulated the “original” high fat diet fordiet induced obesity (DIO) studies in 1996. Today, our high fat
diets are the research standard for DIO mice worldwide.

Contact our Resource Center for valuable insight from morethan 25 years of product experience in the field of obesity.
Let us formulate the diets to meet your specific study needs.

(DIO) Formulas

Custom OpenSource Diets

Protein
Carbohydrate
FatResearch Diets, Inc has pioneered the formulation andproduction of diets leading to obesity in laboratory
animals. Our DIO series diets D12450B, D12451, andD12492 are the most widely used and published highfat diets worldwide. Our scientists specialize in providing
custom purified OpenSource diets. By carefully
designing the diet formula to fit your protocol, you havecomplete control over small or large changes in dietcomposition. Plus you are able to report what youranimals were fed, repeat the formula and revise dietcomposition as necessary.

Incorporate Test Compounds
Research Diets, Inc. will incorporate your test compound
into pelleted diets for simple, safe dosing. Feeding test
compounds eliminates dosing related stress to theanimal, eliminates vehicle effects, and saves time andlabor. Consult with one of our scientists on the formula,determine the dosage required and the diet will beproduced and shipped in 5 to 7 business days.

Value Added Resource
The value of our products is in the scientific support weprovide. Our Resource Center is staffed with Masters andPh.D. level scientists with access to over 14,000 original
formulas and a database of more than 3,800 journal
articles. We welcome the opportunity to talk science withresearchers throughout the world as we maintain ourleadership role as the knowledge base for OpenSource
Diet formulation.

BioDAQ Episodic Intake Monitor
BioDAQ E2 Episodic monitoring system measures thead libitum food and water intake behavior of singly
housed lab rats and mice at very high resolution in theirhome cage. Computer controlled electronics record foodand water intake episodically by measuring the momentto-moment, undisturbed intake behavior of the animals
being studied. The animal’s behavior defines the variable
period for these intake measurements through theirnative behavior.

Product #Total
kcal/gm

D12451
gm% kcal%
2420
41
35
24
45
100
4.73

D12492
gm% kcal%
2026
20
26
60
35100
5.24

IngredientCasein, 80 Mesh
L-Cystine

gm
200
3kcal
800
12gm
200
3kcal
800
12Corn Starch
Maltodextrin 10Sucrose

72.8
100
172.8

291
400
691012568.8

0500275

Cellulose, BW200500500

Soybean Oil
Lard25177.5225
1598252452252205

Mineral Mix S10026
DiCalcium Phosphate
Calcium Carbonate
Potassium Citrate, 1 H2O

10135.5
16.5000010
135.5
16.5

0000

Vitamin Mix V10001
Choline Bitartrate

102400102400

FD&C Red Dye #40

0.05

00.05

0773.854057

FD&C Blue Dye #1
Total

858.154057

Formulated by E. A. Ulman, Ph.D., Research Diets, Inc., 1/18/96 and 8/26/98.
Use D12450B 10% kcal fat as matched control diet.