Dietary Fat, Not Sugar Or Protein, Causes Weight Gain

A large-scale dietary trial in mice shows that fat, not protein or carbohydrate, was responsible for causing obesity.

AsianScientist (Jul. 26, 2018) – Scientists have demonstrated that fat is indeed the cause of obesity, contrary to recent reports suggesting that fat may protect individuals from becoming overweight. Their findings are published in Cell Metabolism.

What we eat plays a big role in our ability to regulate our body weight. Over time, however, different ideas have emerged about the most important dietary factors that cause us to put on weight. During the 1980s and 1990s, it was widely accepted that the most important factor in weight gain is the fat content of our diets.

More recently, some have suggested that this focus on fat was misplaced—carbohydrate intake, especially refined carbohydrates like sugars, was blamed instead.

In this study, scientists at the Institute of Genetics and Developmental Biology in Beijing, China, collaborated with researchers at the University of Aberdeen in Scotland to perform the largest study of its kind to resolve what components of the diet cause mice to put on body fat.

The study included 30 different diets that varied in their fat, carbohydrate and protein contents. Mice of five different strains were fed these diets for three months, which is equivalent to nine years in humans.

In total, over 100,000 measurements were made of the mice’s body weight changes, and their body fat was measured using a micro magnetic resonance imaging machine. The results of this enormous study were unequivocal—the only component in food that made the mice obese was fat. Carbohydrates had no effect, even when they comprised up to 30 percent of calories in the mice’s diet.

Combining sugar with fat had no more impact than fat alone. There was no evidence that low protein levels (as low as five percent of the total calories) stimulated greater food intake. The researchers believe that dietary fat caused weight gain because fat in the diet uniquely stimulated the reward centers in the brain, thus causing greater intake of calories.

“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,” said Professor John Speakman of the University of Aberdeen who led the study.

The article can be found at: Hu et al. (2018) Dietary Fat, but Not Protein or Carbohydrate, Regulates Energy Intake and Causes Adiposity in Mice.


Source: Chinese Academy of Sciences; Photo: Pixabay.
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