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Specific Nutrient Changes May Not Effect Weight Loss

Obesity and being overweight are leading health concerns in the US. Being overweight is considered a risk for chronic diseases such as high blood pressure, heart disease, and diabetes. The general principle of weight loss is to use more calories than one consumes. This means lowering the amount of food eaten and increasing physical activity. However, many still struggle to achieve their weight loss goals. Some believe that the proportions of proteins, carbohydrates, and fats are a key factor to weight loss. This has resulted in a variety of specialized diets that over or under emphasizes a particular nutrient.

The Harvard School of Public Health wanted to clarify what type of nutrient change if any was best in reaching weight loss goals. The study published in the New England Journal of Medicine found no significant difference in weight loss between the diets.

About the Study

The randomized trial followed 811 participants over a two-year period. The participants were all offered group and individual instructional sessions over the study period. Changes were measured by body weight every six months. The participants were split into four groups. Each group was assigned a diet that emphasized carbohydrates, protein, or fat. The diet options were:

  • 20% of calories from fat, 15% from protein, and 65% from carbohydrates
  • 20% from fat, 25% from protein, and 55% from carbohydrates
  • 40% from fat, 15% from protein, and 45% from carbohydrates
  • 40% from fat, 25% from protein, and 35% from carbohydrates

The goal in all four groups was to reduce their caloric intake by 750 calories per day. Researchers recorded weight loss and dietary changes. At the end of the program, on average, all groups lost the same amount of weight. The researchers noted that participants that attended support sessions lost more weight than those that did not attend.

There are some concerns with this study. There was a high dropout rate with only 79.5% of the participants completing the study. The participants also had difficulty adhering to the dietary guidelines that were established. Few reached their dietary goals.

How Does This Affect You?    TOP

Long term adherence to any diet plan is difficult for almost everyone. As seen in this study, many people were unable to stay with the program over the two-year period. Nevertheless, its results are consistent with those of many other studies: as long as calories are kept low, it does not much matter where those calories come from. Reducing overall caloric intake is the key to successful weight loss. The study also confirmed that personal support is an important component of effective behavioral change.

A dietitian can help you make a plan to adjust your current diet. Small gradual changes are easier to accept than a dramatic dietary overhaul. Talk to your doctor before beginning a diet that excludes or emphasizes one nutrient. Diets that restrict specific nutrients can be harmful for some people. Seek support through a weight loss group, family members, or a professional.


American Dietetic Association
The Obesity Society


Sacks FM, Bray GA, Smith SR, et al. Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates. N Engl J Med. 2009 Feb 26;360(9):859-73.
Last reviewed April 2009 by Richard Glickman-Simon, MD

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