There has been a significant amount of debate to whether low-fat or low-carbohydrate is better.

You may remember our previous article about a study comparing these diets with the same amount of calories in both groups tested. That study found that low-fat diets were marginally better than low-carb diets for weight loss. Meanwhile, low-carb diets have been at the forefront of most diet plans, even if there is a lack of long-term studies to prove them more effective than low-fat diets. Furthermore, cardiovascular effects of low-carb diets is not well-studied, particularly in diverse populations.

Study outcome

One of the most comprehensive and well-planned studies by Bazzano et al followed 150 obese men and women for one year, randomly assigned to low-carb or low-fat diets. Half of the participants were white, the other black. None had any history of heart disease or diabetes when the study began. The low-carb group were asked to eat <40 g of carbs a day while the low-fat group were asked to keep total caloric intake from fats at 30%.

Participants attended nutrition courses, but caloric intake wasn’t controlled. The low-carb group lost an average of 5.44 kg while the low-fat group lost 1.81 kg. What’s more, the low-carb group had less inflammation, better cholesterol levels, and improved triglyceride levels. Thus, this study seems to suggest that low-carb diets are superior to low-fat diets for weight loss?

Limitations

Not so fast. Unlike the study in our previous post, this study didn’t control total caloric intake. Nor did it run past a year. We know nothing of what foods the participants actually ate. Rather, we know that giving them various instructions had different effects on their weight. This is why understanding study design is so important when interpreting results. To speculate, the increased weight loss in the low-carb group most likely occurred because they ate higher quality foods. For a healthy heart, it is important to eat a variety of good fat sources and not just binge on margarine. 

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Article by Ali Zamini, MSc Psychology.

Source:
Bazzano et al. Effects of Low-Carbohydrate and Low-Fat Diets: A Randomized Trial. Annals of Internal Medicine 2014.