Shahar Madjar, MD

So many diets, so much controversy. One question waiting for a definite answer is whether diets that differ in the contents of their macronutrients (fat, protein, and carbohydrates) result in different degrees and rates of weight loss. Is it really worthwhile to restrict your diet based on the content of macronutrients? Should you embark on low-carb diets such as Atkins or the Ketogenic diets? Perhaps you should try high-protein diets such as Zone and the Paleo? Or indulge yourself on a carbs-rich diet such as the Ornish diet?

Dr. Frank M. Sacks and his colleagues tried to answer this question. They recruited 811 highly-motivated overweight adult volunteers and randomly assigned them to four diets with different percentages of fat, protein, and carbohydrates (individuals who gave the impression of having “insufficient motivation” were not included in the study). The food items on the four different menus were similar, but the quantities of the different items on these menus varied. For example, everyone was encouraged to eat a poached egg for breakfast. Everyone was also asked to consume 1/2 a cup of cooked red peppers and 1/2 a cup of cooked mushrooms for lunch. But, at lunch, participants in the high-protein group were supposed to eat 2 ounces of cooked boneless turkey while those in the average protein group were not.

Sacks invited the participants to individual and group instructional sessions. Those who attended lost more weight.

Most of the weight loss took place in the first 6 months. At 6 months, the average weight loss in all four groups was similar, 6 kg, or 7% of the initial weight. After 6 months, the different groups started to regain some of their weight, and at two years, those who completed the study (80% of the participants) lost, on average, 4 kg. Some participants had better results with 14-15% of them losing at least 10% of their body weight. And all groups had similar weight loss, sensation of hunger, satiety, and satisfaction with their diet.

Dr. Sacks’ conclusion may sound familiar to some: no matter what the source of your calories are, a calorie is a calorie, a diet is a diet, and if you stick to it, you will lose weight. But a deeper examination of the findings tells a different story:

First, the study design called for the low-carb group to consume significant amount of carbohydrates (35% of their total calories) which is much higher than the amount of carbohydrates recommended by traditional low-carb diets such as the Atkin’s diet. Second, the participants did not fully adhere to their diet recommendations and the diets in the four different groups were more similar to one another than originally planned. For example, protein intake was supposed to differ by 10% between the high- and low-protein groups but, in reality, the difference was only 1-2%. Is it, then, surprising that the weight loss in the four different groups was similar?

Perhaps we can learn from this study less about the role fat, protein, and carbohydrates plays in our diet, and more about human nature. Dr. Sacks’ study was conducted by experienced researchers and published in the prestigious medical publication The New England Journal of Medicine. The participants were carefully selected and highly motivated. Most of them, I am sure, made a sincere effort to adhere to their diet for a long period of time. Yet, the diet plans weren’t followed according to plan, the weight loss was moderate at best, and some of the weight that was lost was regained.

The results in Dr. Sacks’ study are consistent with the results of other studies examining the effect of diet composition on weight loss. A meta-analysis by Long Ge and his colleagues, published in the British Medical Journal in 2020, analyzed the results of 121 randomized trials comparing a usual diet with low carb diets (such as Atkins, Zone), high carb diets (such as Ornish), and balanced diets (such as DASH and Mediterranean diets). Altogether, these 121 studies included 21,942 participants. At 6 months, the diets, any of them, resulted in substantial improvement in cardiovascular risk factors, particularly blood pressure, but the effects of these diets on weight reduction was only modest and similar among the different groups of diets. And at 12 months, the effect on weight loss has diminished and the improvement in cardiovascular risk factors has largely disappeared. The researchers concluded that the differences between diets were typically small to trivial.

These results seem awfully pessimistic. I can see some of my readers resort to depression, others to despair. But fret not, a solution is within reach. A new focus of attention needs to emerge: a change in attitudes toward food and diet, and the adoption of new habits and horizons.

Editor’s note: Dr. Shahar Madjar is a urologist at Aspirus and the author of “Is Life Too Long? Essays about Life, Death and Other Trivial Matters.” Contact him at smadjar@yahoo.com.