A low-fat diet seems to boost dieters' mood more than a low-carbohydrate diet.
Very low-carbohydrate diets are often used to help overweight and obese people lose weight, but the long-term effects on psychological well-being are unclear. To investigate this, researchers randomly assigned 106 overweight and obese adults to follow either a very-low-carbohydrate, high-fat diet or a high-carbohydrate, low-fat diet for one year. They assessed changes in body weight and mood and well-being periodically during and one year after the study ended.
After a year, the dieters lost an average of 14 kilograms, with no difference between the two diet groups. After the first eight weeks, tests showed that dieters in both groups experienced an improvement in their mood. However, most measurements of mood revealed a lasting improvement in only those dieters following the low-fat diet.
The above findings suggest that some aspects of the low-carbohydrate diet may have had damaging effects on mood that, over the term of a year, negated any positive effects of weight loss.