Fat, protein, carbohydrate and energy intake

A crucial issue in food science is to pinpoint exactly what aspect of the typical diet (fat, protein and carbs) leads to weight gain. A significant part of the problem is that it is very difficult to conduct studies on humans for long periods of time where what they eat is controlled. However this is feasible in animal studies that are similar to humans.

Scientists from UK and Chinese institutions conducted a mice study that includes 30 different diets that vary in their fat, carbohydrate (sugar) and protein contents.The mice were fed the different diets for three months, which is equivalent to nine years in humans. In total over the researchers made more than 100,000 measurements in body weight changes and the body fat of mice.

The results of the study revealed that the only thing that made the mice gaining weight was eating more fat in the diets. According to Professor John Speakman, a member of the scientific team of the study: “Carbohydrates including up to 30% of calories coming from sugar had no effect. Combining sugar with fat had no more impact than fat alone. There was no evidence that low protein (down to 5%) stimulated greater intake, suggesting there is no protein target. These effects of dietary fat seemed to be because uniquely fat in the diet stimulated the reward centers in the brain, stimulating greater intake.

“A clear limitation of this study is that it is based on mice rather than humans. However, mice have lots of similarities to humans in their physiology and metabolism, and we are never going to do studies where the diets of humans are controlled in the same way for such long periods. So the evidence it provides is a good clue to what the effects of different diets are likely to be in humans.”

Source:

Hu, S.; Wang, L.; Yang, D.; Li, L.; Togo, J.; Wu, Y.; Liu, Q.; Li, B.; Li, M.; Wang, G.; et al. (2018). Dietary fat, but not protein or carbohydrate, regulates energy intake and causes adiposity in mice. Cell Metab, 28, 415–431.e4.