I frequently talk to people who believe that a vegetarian lifestyle is healthier and that animal proteins and fats should be avoided. The evidence to support these claims is weak at best and completely refuted by many sources.
The A To Z Trial was published in the Journal of the American Medical Association (JAMA) in March, 2007. This trial compared 4 diets:
- The Atkins Diet – low carb, high protein, & high fat. Dr Atkins’ New Diet Revolution.
- Traditional (Lifestyles, Exercise, Attitudes, Relationships, & Nutrition – LEARN) Diet – a ‘prudent’ diet that included 55% to 60% energy from carbohydrate and less than 10% energy from saturated fat, caloric . restriction, increased exercise, and behavior modification strategies. The LEARN Manual for Weight Management.
- Ornish Diet – no more than 10% of energy from fat, very high carbs. Eat More, Weigh Less.
- Zone Diet – 40% carbs, 30% protein, & 30% fat. Enter the Zone.
Each group followed the recommendations of their respective books (written in italics above). Basically, this study compared the effects of low-carb and low-fat and the results are self-explanatory.
311 premenopausal were randomized (by drawing names out of a hat, no joke) to the 4 different groups listed above. Each group received the same education on their specific diet by the same educator. Outcomes were measured as:
- Weight loss at 12 months (primary outcome, the others listed are secondary outcomes)
- Lipid profile (LDL, HDL, non-HDL, and Triglycerides)
- % body fat
- waist-hip ratio
- fasting insulin
- fasting glucose
- blood pressure
So what were the outcomes? Atkins was as good as or better in every metric compared to the other diets!
Weight Loss, % Body Fat, & Waist-Hip Ratio
The winner = Atkins
Weight lost at 12 months
- Atkins – 4.7 kg (10.34 lbs)
- LEARN – 2.2 kg (4.84 lbs)
- Ornish – 2.6 kg (5.72 lbs)
- Zone – 1.6 kg (3.52 lbs)
(All of these numbers are reported in mg/dL)
HDL & Triglycerides (TGs) winner = Atkins
- Atkins – increased HDL 4.9 mg/dL, decreased TGs 29.3 mg/dL
- LEARN – increased HDL 2.8, decreased TGs 14.6
- Ornish – increased HDL 0 (yes, thats a zero), decreased TGs 14.9
- Zone – increased HDL 2.2, decreased TGs 4.2
LDL & non-HDL winner = Ornish
- Atkins – increased LDL 0.8, decreased non-HDL 5.1
- LEARN – increased LDL 0.6, decreased non-HDL 4.0
- Ornish – decreased LDL 3.8, decreased non-HDL 6.8
- Zone – no change in LDL, decreased non-HDL 0.5
Insulin & Glucose
Insulin & Glucose winner = Atkins (though the results did not reach statistical significance)
- Atkins – decreased insulin 1.8, decreased glucose 1.8
- LEARN – decreased insulin 1.8, increased glucose 0.5
- Ornish – decreased insulin 0.5, decreased glucose 0.8
- Zone – decreased insulin 1.5, decreased glucose 1.6
Blood pressure winner = Atkins
Blood pressure was improved in each group. Systolic/diastolic pressure decrease is reported in mm Hg.
- Atkins – 7.6/4.4
- LEARN – 3.1/2.2
- Ornish – 1.9/0.7
- Zone – 3.3/2.1
So for those of you who fear fat, bacon, butter, lard, and meat and believe that carbs, whole grains, and avoidance of fat in your diet is the way to do, think again. The scientific evidence simply is not in favor of these beliefs.
This study was published in JAMA yet, ironically, the dietary advice of the American Medical Association is to avoid fat and eat carbs. When will they start listening to their own data?
Here is the link to the original study: Comparison of the Atkins, Zone, Ornish, and LEARN Diets for Change in Weight and Related Risk Factors Among Overweight Premenopausal WomenThe A TO Z Weight Loss Study: A Randomized Trial.