There is a lot of contention over whether the source of a calorie matters or if counting calories is all that matters. One camp argues that calories from certain sources, such as carbohydrates, are worse for you in terms of weight loss. Another camp believes that calories are calories and it doesn’t matter where they come from, just make sure the total number is within limits. Who’s right? Good question. But a recent study* challenges the notion that a “calorie is a calorie.”
The study was led by Cara Ebbeling, PhD, Associate Director and David Ludwig, MD, director of the New Balance Foundation Obesity Prevention Center in Boston and published on June 26 in the Journal of American Medical Association. The results of the study suggest that diets that reduce the surge in blood sugar after a meal—either low-glycemic index or very-low carbohydrate—may be preferable to low-fat diets for achieving long-term weight loss. The study also found that the low-glycemic index diet had similar metabolic benefits to the very low-carbohydrate diet without negative effects of stress and inflammation as seen by participants consuming the very low- carbohydrate diet.
The study consisted of 21 adults, ages 18-40. They were tasked with losing 10-15% of their body weight, and after they reached their goal, to complete all three of the following diets in random order, each for four weeks at a time: A low fat diet (which emphasizes reduced dietary fat and increased consumption of whole grains and fruits and vegetables), a low glycemic index diet (including minimally processed grains, vegetables, healthy fats and increased protein) and a low-carbohydrate diet (modeled after the Atkins diet, composed of daily consumption of 10% carbohydrates, 60% fat and 30% protein).
The results? The very low carbohydrate diet produced the biggest improvements in metabolism, but it also increased cortisol levels. Elevated cortisol levels can lead to insulin resistance and cardiovascular disease. It also increased C-reactive protein levels, which may also increase the risk of cardiovascular disease.
The low-fat diet showed the least promise. It produced the greatest decrease in energy expenditure, an unhealthy lipid pattern and insulin resistance.
The low-glycemic index diet showed the most promise when balanced with the disadvantages of the low-carb diet. Not only did it NOT increase cortisol levels, the researcher also feel that it is easier for people to stick with. It doesn’t eliminate entire classes of food so people feel less deprived and more in control.