May 9, 2023

Lesson from New England Journal of Medicine Study: Diet without Lifestyle Change is Not Enough



You may have seen the headlines last week. Something like: Type of Diet Doesn’t Matter.

A very large new study in the prestigious New England Journal of Medicine generated all of these headlines.

In the study, 811 middle class overweight adults participated in one of four diet programs, low-fat, low-carb, etc. After two years, every diet group had lost – and regained – about the same amount of weight regardless of what diet had been assigned. Participants lost an average of 13 pounds at six months and had maintained about 9 pounds of weight loss and a two-inch drop in waist size after two years. While the average weight loss was modest, about 15% of dieters lost more than 10% of their weight by the end of the study. Still, after a few months, most returned to at least some of their usual eating habits.

The media picked up on one important finding: Participants on the different diets achieved the same results.

However, it should be noted that those in the “low-fat” diet group actually consumed about 26% of their calories from fat. The scientific literature on diets defines this as a “moderate fat diet.”1 At Wellspring, we use a very low-fat diet (<10% calories from fat). As a result, there’s a strong argument that the study sheds no light on the relative merits of a low-fat or a very low-fat diet vs. other diets that involve a much higher percentage of calories from fat. Other studies consistently show the benefits of low fat and very low fat diets.2 -5

More important, the overall outcomes were not particularly impressive: an average of 9 lbs. weight loss (out of an average of 50 lbs of excess weight at the start) after dieting for two years.

In the accompanying editorial, Dr. Martijn Katahn stated: “It is obvious by now that weight losses among participants in diet trials will at best average 3-4 kg after 2-4 years.”

We agree. Diets are largely ineffective. Becoming a successful weight controller clearly involves far more than changing the macronutrients in the diet. Weight loss is complex and behavioral in nature, and requires a coordinated and systematic plan of attack. At Wellspring, we provide a much more intensive approach with trained therapists who use cognitive-behavior therapy to help participants improve: commitment, self-awareness, focusing, emotional awareness, and stress management. Also, even more significantly perhaps, we use theimmersion process to help guarantee a great deal of initial success – including staff modeling, peer support, and enough control of diet and activity to promote dramatic change. These dramatic changes lead to tremendous enthusiasm by participants and their families. This kind of success probably improves self-efficacy (believing that they really can change) and may increase the families’ willingness to embrace the approach at home.

In his editorial, Dr. Katahn reviewed a fascinating new study in a two communities in France that essentially immersed both communities in an effort to change lifestyle – diet and activity and attitude. This approach bears a striking resemblance in key ways to Wellspring’s communities.

So the important message of The New England Journal of Medicine study is not that low-carb diets works as well as low-fat diets (moderate fat diets in this case). It’s that diets don’t work. No diet can produce the changes in attitude, skills, support and behaviors that long-term weight control requires.

The New England Journal of Medicine study is entitled “Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein, and Carbohydrates.” You can read this paper and the accompanying editorial by Dr. Katahn by going to the following links:

Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein, and Carbohydrates

Weight-Loss Diets for the Prevention and Treatment of Obesity


  1. Freedman MR, King J, Kennedy E. Popular diets: a scientific review. Obesity Research. 9; 1S-40S.
  2. Shick SM, Wing RR, Klem ML, McGuire MT, Hill JO, Seagle HM. Persons successful at long-term weight loss and maintenance continue to consume a low-energy, low-fat diet. J Am Diet Assoc. 1998;98;408-413. .
  3. Bray GA, Popkin BM. Dietary fat intake does affect obesity! Am J Clin Nutr. 1998;68:1157-73. .
  4. Kirschenbaum DS. Very low fat diets are better than low carb diets: A commentary based on science. Patient Care. 2005;39:47-55. .
  5. Astrup A. Grunwald GK, Melanson EL, Saris WHM, Hill JO. The role of low-fat diets in body weight control: a meta-analysis of ad libitum dietary intervention studies. Int J Obes. 2000;24:1545-1552.