Low Carb v Low Fat: What if Neither Diet Works For You?

Are you on a Paleo diet, a South Beach diet, a feast and famine diet, or an all-the-chocolate you can eat diet (I made this one up)? There are so many diets from which to choose where all give evidence of success, with the participants claiming increased energy, decreased blood pressure, and no hunger. Sometimes specific foods, rather than the diet, are given credit for the weight loss: the dieter stops eating all white foods, gives up eating fruits with pits in them, drinks only milk that comes from nuts, stops eating all fried food, or eats only fried foods. Arguments about the virtue or uselessness of various diets cause unwinnable arguments, because one person’s weight loss is someone else’s failure.

Now the arguments can stop. Recently, newspaper and publications on health matters reported the results of a 12-month weight-loss trial that seemed to halt discussions of “my diet is better than yours.” Published in JAMA, the study presented the results of a year-long weight-loss study in which the 609 participating adults were assigned to a either a low-fat or a low- carbohydrate diet. (“Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion,” The DIETFITS Randomized Clinical Trial, Gardner, C. , Trepanowski, J., Del Gobbo, L., JAMA, 2018;319(7):667-679.) At the end of the study period,their weight loss was similar.

The foods on the low-fat and the low-carbohydrate diets were carefully regulated; only healthy fats like avocado and nuts, and healthy carbs such as whole grains, lentils and beans, were allowed. The operative word influencing food choice was healthy. Both groups were encouraged to eat large quantities of fresh vegetables and instructed as to how to prepare foods that were relatively unprocessed.

The amount of weight loss was moderate; both groups lost about 6 kg, or about 13 pounds, in 12 months. This amount of weight loss cannot compete with claims made in television advertisements or tabloid magazine articles for commercial diets. However, unlike the “quick weight-loss” promises of such programs, the diets in the research study produced the type of weight loss that can be sustained over long periods of time and maintained after weight-loss goals are attained. Indeed, the food choices in both diets were similar to those recommended for everyone in order to avoid heart disease and diabetes.

But will this news make an impact on diet programs? Will it stop self-appointed nutrition experts from claiming that their method of weight loss is optimal? Will it decrease the claims that a particular herb, hormone, mineral, spice or berry has the power to alter metabolism so that weight will be lost easily? Might it stop celebrities from self-righteous statements about their total avoidance of a particular food group, usually carbohydrates but sometimes most food , in order to attain a perfect body? Probably not, because the diet plans tested were sensible, not sensational, and unlikely to sell tabloid magazines, books or magazines promoting the latest way to lose weight.
But there are reasons why the results from this study should not close the discussion on the best way to lose weight. People who suffer from morbid obesity often need an intervention that produces more than a 13 pound weight loss per year. Surgery that reduces the size of the stomach may be the only effective solution with the type of diet subsequently followed designed to ensure that patients eat enough protein. Besides, the JAMA study diets that include bulky vegetables, whole grains and other high-fiber foods may not be suitable for stomachs that can hold only tablespoon quantities of food after surgery. Of course eventually, when the stomach can receive larger quantities of food, patients might be able to follow the JAMA diets.

Obesity associated with emotional overeating, especially binge eating that is often linked to anxiety, will not respond to any dietary intervention without sufficient psychological counseling. When and if the emotional component no longer causes excessive food intake, then either low-fat or low-carbohydrate food plans may work.

Weight gained as a side effect of psychotropic drug treatment may be hard to reverse with either of the diets described in the JAMA article. Anti-depressants and related drugs cause a persistent craving for carbohydrates along with the absence of satiety. Patients who rarely had weight issues prior to treatment struggle to overcome their medication-induced need to eat. So far the only dietary intervention that increases satiety and decrease carbohydrate cravings is one which allows a small snack of carbohydrate to be consumed prior to meals and sometimes between meals. The carbohydrate increases brain serotonin which in turn increases satiety and turns off craving. Since the subjects in the JAMA study were not on such medications, there is no way of knowing if either or both diets might have been effective.

The weight-loss program in the study educated the participants in healthy meal preparation. In an ideal world, dieters have time to do just this: shop for the right foods, prepare them and clean up after the meal. One hopes that the advice and training given the participants also included what to eat when staying late at work, dealing with sick children, car pools, long commutes, bad weather, travel, holidays and other often unavoidable situations that make it difficult to make the right food choices.

However, the study presents the hopeful possibility of stopping the arguments over which type of diet is best. Now future studies can focus on the best weight-loss intervention for those whose weight loss may not respond to conventional diets and on how best to help the dieter adhere to whatever program is recommended.

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