Obesity: Calories or content: what is the best weight-loss diet?

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source : http://www.nature.com/nrendo/journal/v5/n8/full/nrendo.2009.145.html#top

Nature Reviews Endocrinology 5, 419-420 (August 2009) | doi:10.1038/nrendo.2009.145

Subject Categories: Nutrition | Obesity

Obesity: Calories or content: what is the best weight-loss diet?
Jonathan Q. Purnell1  About the author


Researchers have randomly assigned 811 overweight adults to low-calorie diets with differing percentages of energy derived from protein, carbohydrate, and fat; participants were followed up for 2 years. All groups experienced modest weight loss and improvements in cardiac and diabetes risk factors. Does this finding mean that clinicians can finally advise their patients on the best way to lose weight?

Most overweight and obese patients and their clinicians remain alert for 'the' diet that results in meaningful and sustained weight loss. The most obvious answer is to simply eat less. This advice is logically satisfying as energy balance is clearly tipped in a negative direction, at least temporarily, and serves as a conveniently simple treatment sound-bite for a 15 min doctor's visit. However, evidence that meaningful weight loss is sustained for more than a few years following a low-calorie diet is hard to find.¹ The reason for this lack of sustainability is thought to include both environmental influences and a complex regulatory system in the body, which is geared towards limiting weight loss during hypocaloric states and restoring baseline body weight, even when that baseline weight is considered socially and medically undesirable.²

Poor long-term outcomes with caloric restriction alone have given rise to advocation of increased consumption or elimination of specific food elements instead, typically a macronutrient in the diet such as fat, carbohydrate or protein. New diet claims routinely come out, are adopted by a public eager for an effective weight-loss treatment, and inevitably fall by the wayside. Recently, investigators from three major nutritional research centers in the US reported their findings on weight loss and health outcomes in overweight and obese individuals assigned to reduced-calorie diets that contained different macronutrient compositions.³

In this study by Sacks and co-investigators,³ one of the largest such comparator studies to date, 811 patients followed diets that aimed to achieve a caloric deficit of 750 kcal per day, calculated from their energy expenditure and activity level at baseline. Participants were randomly allocated to one of four diets that differed in the percentage of total calories from different macronutrients: 20% fat (low fat), 15% protein (average protein) and 65% carbohydrate (high carbohydrate); 20% fat, 25% protein (high protein) and 55% carbohydrate; 40% fat (high fat), 15% protein and 45% carbohydrate; or 40% fat, 25% protein and 35% carbohydrate (low carbohydrate). Despite the notoriously high dropout rate of 40% for most dietary studies, a remarkable 80% of participants completed 2 years of follow-up.

In the subset of participants who provided dietary information at baseline, intake of fat as a percentage of total calories was relatively high at 37%, which is similar to that reported in population studies a decade ago.⁴ This finding indicates that the average US diet has been remarkably stable for years. At the end of 2 years, individuals assigned to the low-fat diets had successfully lowered their fat intake to roughly 27%; however, those assigned to the high-fat diets had also lowered their average fat intake to 33–35%, instead of the study target of 40%. While this difference enabled a comparison of the effects of high-fat and low-fat intakes, in actuality both groups might have experienced partial weight loss as a result of their reduced fat intake. In addition, the hoped-for comparison between an average-protein diet (15% of total calories) and a high-protein diet (25% of total calories) was not successful. Both these groups ended up increasing their average protein intake from 18% at baseline to between 20% and 21% after 2 years.

The patterns of weight loss for all combinations of diet comparisons were similar, with an average nadir loss of 6 kg by 6 months and slow, steady, weight regain thereafter; by the study end, participants were on average 4 kg below their baseline weight. Not unexpectedly, attendance at the regular group sessions that promoted dietary adherence was associated with increased weight loss. In addition, the 2 x  2 factorial design of the study meant that self-reported intake of each dietary macronutrient could be used to test the effect of each goal on weight loss. Adherence to the protein-intake goal was related to increased weight loss in the high-protein but not the average-protein groups, and adherence to the fat-intake goal was related to increased weight loss in the low-fat but not the high-fat group. This same factorial analysis was used to compare changes in cholesterol levels between the diets by differing macronutrient content: after 2 years, both total and LDL-cholesterol levels were lower when participants ate fewer calories as fat and more as carbohydrates, but HDL cholesterol did not improve (increase) to a similar extent in those who ate the highest proportion of carbohydrates. Variations in protein consumption did not significantly affect any metabolic outcome, although the lack of any significant effect may have been because of the limited difference in percentage protein between the diets.

With weight loss, all diets resulted in decreased levels of total and LDL cholesterol, increased levels of HDL cholesterol, and improvements in insulin levels and homeostasis model assessment (HOMA) scores for insulin sensitivity. What did not happen is also worth noting. High-fat diets did not result in catastrophic deterioration of glucose and lipid metabolism, and high carbohydrate levels, long thought by some to be the agent of weight gain and diabetes, did not elevate triglyceride or insulin levels or result in deterioration of HOMA scores.

A better dietary comparator trial than this one is unlikely to be conducted in the foreseeable future in terms of the number of participants enrolled, study design, low dropout rate, and the provision of dietary counseling and behavioral intervention. When these results are combined with similar findings of other recent diet comparator studies,^{5, 6, 7} the take-home messages become clearer. First, the average weight loss on any diet, regardless of the macronutrient content, is very modest (about 2–4 kg in total) and certainly does not back up the claims of dramatic results usually made by commercial products. This point is especially important for patients, as unrealistic weight-loss expectations can lead to frustration and abandonment of diets that clearly improve or prevent chronic diseases such as diabetes.⁸ Second, regardless of the diet content, weight loss improves lipid levels, inflammatory markers, and glucose levels.

This study did not, however, address a number of important issues, including a description of the range of individual weight changes by diet assignment. Dansinger et al. showed that regardless of assignment to a low-calorie, low-fat, low-carbohydrate, or high-protein diet, individual weight changes at 1 year varied greatly, from weight gain in some participants to marked weight loss in others.⁵ If determinants of individual responsiveness could be identified, clinicians might be able to tailor dietary advice on macronutrient content to optimize each patient's weight-loss potential. In addition, no exercise arm was included. Along with diet, exercise is often included as a standard clinical recommendation for obese patients and may improve their chances of sustained weight loss.⁹ Finally, as raised by the accompanying editorial to the discussed paper,¹⁰ the results of this study do not answer the question of what is the optimal dietary macronutrient composition to prevent onset of unwanted weight gain and obesity, a far more important consideration from a public health standpoint.

Practice point

• Weight loss on low-calorie diets is modest, typically 2–4 kg after 2 years
• A high fat intake raised HDL-cholesterol levels the most, while a high carbohydrate intake best lowered LDL cholesterol
  
• Regardless of macronutrient content, modest weight loss improves risk factors for cardiovascular disease and diabetes
  

*Competing interests statement
The author declares no competing interests.


References

1.Tsai, A. G. & Wadden, T. A. Systematic review: an evaluation of major commercial weight loss programs in the United States. Ann. Intern. Med. 142, 56–66 (2005).PubMed

2.Morton, G. J., Cummings, D. E., Baskin, D. G., Barsh, G. S. & Schwartz, M. W. Central nervous system control of food intake and body weight. Nature 443, 289–295 (2006).ArticlePubMedISIChemPort

3.Sacks, F. M. et al. Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates. N. Engl. J. Med. 360, 859–873 (2009).ArticlePubMedChemPort

4.Ernst, N. D., Sempos, C. T., Briefel, R. R. & Clark, M. B. Consistency between US dietary fat intake and serum total cholesterol concentrations: the National Health and Nutrition Examination Surveys. Am. J. Clin. Nutr. 66, S965–S972 (1997).

5.Dansinger, M. L., Gleason, J. A., Griffith, J. L., Selker, H. P. & Schaefer, E. J. Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction: a randomized trial. JAMA 293, 43–53 (2005).ArticlePubMedISIChemPort

6.Shai, I. et al. Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. N. Engl. J. Med. 359, 229–241 (2008).ArticlePubMedChemPort

7.Gardner, C. D. et al. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A to Z Weight Loss Study: a randomized trial. JAMA 297, 969–977 (2007).ArticlePubMedISIChemPort

8.Knowler, W. C. et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N. Engl. J. Med. 346, 393–403 (2002).ArticlePubMedISIChemPort

9.Klem, M. L., Wing, R. R., McGuire, M. T., Seagle, H. M. & Hill, J. O. A descriptive study of individuals successful at long-term maintenance of substantial weight loss. Am. J. Clin. Nutr. 66, 239–246 (1997).PubMedISIChemPort

10.Katan, M. B. Weight-loss diets for the prevention and treatment of obesity. N. Engl. J. Med. 360, 923–925 (2009).

ArticlePubMedChemPort


Author affiliations
1.Division of Endocrinology, Diabetes, and Clinical Nutrition, Oregon Health & Science University, OR, USA.
Correspondence to: J. Q. Purnell, Division of Endocrinology, Diabetes, and Clinical Nutrition, Oregon Health and Science University, Mail Stop L481, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
Email: purnellj [at] ohsu.edu

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             For me the best, common, cheap best weight-loss diet is through exercise.


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