Effects of 4 weight-loss diets differing in fat, protein, and carbohydrate

[hailtotheking]

Another good one from this months AARR:

Effects of 4 weight-loss diets differing in fat, protein, and carbohydrate on fat mass, lean mass, visceral adipose tissue, and hepatic fat: results from the POUNDS LOST trial

Quote

Effects of 4 weight-loss diets differing in fat, protein, and carbohydrate on fat mass, lean mass, visceral adipose tissue, and hepatic fat: results from the POUNDS LOST trial1,2,3

Russell J de Souza, George A Bray, Vincent J Carey, Kevin D Hall, Meryl S LeBoff, Catherine M Loria, Nancy M Laranjo, Frank M Sacks, and Steven R Smith
+ Author Affiliations

1From the Department of Nutrition, Harvard School of Public Health, Boston, MA (RJdS and FMS); the Pennington Biomedical Research Center, Baton Rouge, LA (GAB and SRS); the Channing Laboratory (FMS, VJC, and NML) and Endocrine Division (MSL), Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA; the Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD (KDH); and the National Heart, Lung, and Blood Institute, Bethesda, MD (CML).
+ Author Notes

↵2 Supported by the National Heart, Lung, and Blood Institute (grant HL073286) and the General Clinical Research Center, NIH (grant RR-02635).

↵3 Address correspondence to GA Bray, 6400 Perkins Road, Baton Rouge, LA 70808. E-mail: brayga@pbrc.edu.

Abstract

Background: Weight loss reduces body fat and lean mass, but whether these changes are influenced by macronutrient composition of the diet is unclear.

Objective: We determined whether energy-reduced diets that emphasize fat, protein, or carbohydrate differentially reduce total, visceral, or hepatic fat or preserve lean mass.

Design: In a subset of participants in a randomized trial of 4 weight-loss diets, body fat and lean mass (n = 424; by using dual-energy X-ray absorptiometry) and abdominal and hepatic fat (n = 165; by using computed tomography) were measured after 6 mo and 2 y. Changes from baseline were compared between assigned amounts of protein (25% compared with 15%) and fat (40% compared with 20%) and across 4 carbohydrate amounts (35% through 65%).

Results: At 6 mo, participants lost a mean (±SEM) of 4.2 ± 0.3 kg (12.4%) fat and 2.1 ± 0.3 kg (3.5%) lean mass (both P < 0.0001 compared with baseline values), with no differences between 25% and 15% protein (P ≥ 0.10), 40% and 20% fat (P ≥ 0.34), or 65% and 35% carbohydrate (P ≥ 0.27). Participants lost 2.3 ± 0.2 kg (13.8%) abdominal fat: 1.5 ± 0.2 kg (13.6%) subcutaneous fat and 0.9 ± 0.1 kg (16.1%) visceral fat (all P < 0.0001 compared with baseline values), with no differences between the diets (P ≥ 0.29). Women lost more visceral fat than did men relative to total-body fat loss. Participants regained ∼40% of these losses by 2 y, with no differences between diets (P ≥ 0.23). Weight loss reduced hepatic fat, but there were no differences between groups (P ≥ 0.28). Dietary goals were not fully met; self-reported contrasts were closer to 2% protein, 8% fat, and 14% carbohydrate at 6 mo and 1%, 7%, and 10%, respectively, at 2 y.

Conclusion: Participants lost more fat than lean mass after consumption of all diets, with no differences in changes in body composition, abdominal fat, or hepatic fat between assigned macronutrient amounts. This trial was registered at clinicaltrials.gov as NCT00072995.

[NU_nutrition_TS]

If this is the study I am thinking of, it has been roundly dissected on the paleo/low carb blogs. Certainly some of the figures used in their statistical analysis don't add up if you look at the data in the full text! Also, one of the authors, George A. Bray, is notoriously biased (mind made up) that obesity is purely a function of 'calories in, calories out'.

[hailtotheking]

This is another study showing that differing macronutrient profiles don't have any differing effects on body composition. However this one is looking at the effects in a calorie deficit (i.e dieting). Again, it had a large study group and long duration.

In the first 6 months there was slightly greater lean mass loss in the lower protein, and higher carb, groups, but that trend disappeared in the long run, and the net result was pretty much the same in all groups at the end of the study.

However, there was a few major problems with this study.

The dietary intake was self reported, and the less than expected weight loss rate is probably the result of the tendency for overweight people to under report their food intake.

The other issue was that many of the subjects failed to hit the macronutrient targets originally laid out on the study design. The original study design was to have differences of around 10%, 20%, and 30% between amounts of protein, fat, and carbs, respectively; but what actually happened was self-reported dietary intake showed contrasts of only 2%, 8%, and 14% at 6 months, and 1%, 7%, and 10% at 2 years, respectively.

Note that protein was the macro that had the worst adherence for trying to hit the required target amounts. This in my opinion is yet another indication that eating massive amounts of protein is instinctively unpalatable and unnatural, and if you leave people to instinctively self-select their food they will typically not go for large protein intakes. Animal studies across a wide range of species examining self-regulated protein intake has shown that, across the board, high protein intake as a % of calories is not instinctively chosen.

[hailtotheking]

Nu, i was writing my appraisal as you posted , so you beat me to it as the first commenter!

Yes, the study is pretty flawed, but cant be entirely dismissed. Personally, I was more interested in the self-selection of protein issues.

[NU_nutrition_TS]

Actually, I think we may be talking about different studies - groups of researchers sometimes perform follow-up studies to earlier ones or mine the data collected in an earlier study to do a slightly different analysis.

The study I was thinking of was more tightly controlled but had fewer participants and was of a shorter duration/follow up.