Calorie Reduction Versus Diet For Weight Loss

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Main Category: Nutrition / Diet
Also Included In: Obesity / Weight Loss / Fitness
Article Date: 26 Feb 2009 - 3:00 PST

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A new US study concluded that as long as a diet is heart-healthy and reduces calorie intake it helps you lose weight, no matter what proportions of fat, protein or carbohydrate it contains. However, in an accompanying editorial a nutrition expert questioned the conclusions because the differences between the diets tested were actually much smaller than the researchers had planned, and there was also a tendency for the participants to start putting weight back on again toward the end of the 2 year trial.

The study was the work of researchers from the Preventing Overweight Using Novel Dietary Strategies (POUNDS LOST) study, and was based at Harvard University School of Public Health in Boston, Massachusetts, and at the Pennington Biomedical Research Center of Louisiana State University in Baton Rouge, Louisianna to reflect the diverse range of culinary preferences from the two regions.

The study was published online in the 26 February issue of the New England Journal of Medicine and was funded by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health.

The last few decades have seen an unprecedented surge in different kinds of diet for weight loss, with different emphases on protein, fat and carbohydrate intake, but there are no prolonged studies that compare the relative advantages of such regimens.

For this study the researchers randomly assigned 811 overweight adults aged 30 to 70 to one of four diets, each with different calorie targets for fat, protein and carbohydrate, as follows:

• Low-fat, average protein: 20 percent fat, 15 percent protein, 65 percent carbohydrate.


• Low-fat, high protein: 20 percent fat, 25 percent protein, 55 percent carbohydrate.


• High-fat, average protein: 40 percent fat, 15 percent protein, 45 percent carbohydrate.


• High-fat, high-protein: 40 percent fat, 25 percent protein, 35 percent carbohydrate.

The diets had similar foods and met recognized healthy heart guidelines (low in saturated fat and cholesterol while high in dietary fiber). The participants also had group (twice a month) and individual (every two months) counselling for 2 years.

The participants' targets for daily calorie intake ranged from 1,200 to 2,400 a day so that each person's allowance was less than his or her daily need.

38 per cent of the participants were men and 22 per cent represented ethnic minorities. They were all asked to do a moderate level of exercise, like brisk walking, for at least 90 minutes a week, and none had diabetes or severe heart disease, although some had other risk factors such as high blood pressure or high cholesterol.

The researchers measured weight loss after 6 months and 2 years. The main outcome measure was the change in body weight after 2 years according to type of diet.

The results showed that:

• After 6 months, participants on each diet had shed an average of 6 kg (13.2 lbs) which was about 7 per cent of their starting weight.


• The participants began to regain weight after 12 months.


• 80 per cent of the participants completed the trial and after 2 years the average weight loss was 4kg (8.8 lbs).


• After 2 years, the weight loss across the groups was very similar, regardless of fat, protein and carbohydrate content of their diet.


• Weight loss in those on 15 per cent protein was similar to those on the 25 per cent protein (3.0 and 3.6 kg respectively).


• Weight loss in those on 20 per cent fat was the same as those on 40 per cent fat (3.3 kg for both).


• And in those on 65 per cent carbohydrate and 35 per cent carbohydrate the weight loss was also similar (2.9 and 3.4 kg respectively).


• 14 to 15 per cent of participants lost at least 10 per cent of their initial body weight over the 2 years.


• Attendance at counselling sessions, satiety, hunger, and satisfaction with the diet were similar in all groups.


• Attendance at counselling sessions was strongly linked to weight loss: 0.2 kg per session attended.


• All the diets reduced risk factors due to blood fats and fasting levels of insulin.


• Both at six months and two years, the improved risk factors included reduced levels of triglycerides, LDL (bad) cholesterol, lowered blood pressure, and increased HDL (good) cholesterol.


• All the diets also reduced presence of metabolic syndrome, a cluster of related conditions that includes: being overweight, having high triglycerides, high blood sugar, high blood pressure, and low HDL cholesterol, which increases heart disease risk.


• Participants also reduced their waistlines by 1 to 3 inches by the end of the study.

The authors concluded that:

"Reduced-calorie diets result in clinically meaningful weight loss regardless of which macronutrients they emphasize."

Dr Elizabeth G. Nabel, director of NHLBI said in a press statement that:

"These results show that, as long as people follow a heart-healthy, reduced-calorie diet, there is more than one nutritional approach to achieving and maintaining a healthy weight."

"This provides people who need to lose weight with the flexibility to choose an approach that they're most likely to sustain -- one that is most suited to their personal preferences and health needs," she added.

Co-author Dr Catherine M. Loria, a nutritional epidemiologist at NHLBI said they were "encouraged that, in addition to achieving and maintaining weight loss, study participants experienced other positive health changes as well".

"The findings emphasize the importance of weight loss in reducing heart disease risk," she said.

Dr Frank M. Sacks, principal investigator of POUNDS LOST and Professor of Cardiovascular Disease Prevention in the Nutrition Department at the Harvard School of Public Health, said:

"This new information should focus weight loss approaches on reducing calorie intake rather than any particular proportions of fat, protein or carbohydrate."

"This is important information for health professionals who prescribe weight loss for their patients, and for adults who are seeking ways to sustain a healthful eating pattern," he added.

However, at least one expert remained sceptical about whether the study really did compare the diets as effectively as the researchers had anticipated.

In an accompanying editorial, titled Weight-Loss Diets for the Prevention and Treatment of Obesity, Dr Martijn Katan, a nutrition professor at the Institute of Health Sciences, VU University, Amsterdam, wrote that based on his calculations of their figures, the contrasts between high and low protein, fat and carbohydrate in the diets varied much less than the researchers had planned.

For example the protein levels were supposed to vary by 10 per cent and only did so by 1 or 2 per cent and the difference in carbohydrate count was supposed to be 30 per cent and only 6 per cent was actually achieved.

Katan said the study didn't show that the diets had the same result but rather reinforced findings already established a number of times, that people find it very hard to keep the weight loss in the long term:

"Even these highly motivated, intelligent participants who were coached by expert professionals could not achieve the weight losses needed to reverse the obesity epidemic," explained Katan.

He suggested in terms of public intervention it might be better to address the community rather than the individual, such making sure there are good facilities to encourage people to exercise and avoid unhealthy eating.

"The most important determinant of success might not be the composition of the diet. It might be whether your community promotes exercise and curbs high-calorie foods," he wrote.

"Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein, and Carbohydrates."
Sacks, Frank M., Bray, George A., Carey, Vincent J., Smith, Steven R., Ryan, Donna H., Anton, Stephen D., McManus, Katherine, Champagne, Catherine M., Bishop, Louise M., Laranjo, Nancy, Leboff, Meryl S., Rood, Jennifer C., de Jonge, Lilian, Greenway, Frank L., Loria, Catherine M., Obarzanek, Eva, Williamson, Donald A.
N Engl J Med 2009 360: 859-873.
Published online, February 26, 2009.

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Sources: NEJM article and editorial, NHLBI press release.

Written by: Catharine Paddock, PhD
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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