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'Proof' it's fats, not carbs, that cause weight gain – but only in mice

"Fat consumption is the only cause of weight gain!" declares the Mail Online, reporting on a study where mice were exposed to different diets and monitored for weight gain and increased energy intake.

Around 30 different diets, all highly controlled, were given to mice over a period of 12 weeks.

The diets varied in the amount of carbohydrate, fat and protein they contained. The mice's body composition and food intake was measured every day.

Mice who consumed a steady amount of protein but an increasing amount of dietary fat gained the most body fat during the study.

There was no change in body fat gain when the researchers gave mice increasing amounts of carbohydrates while they ate steady amounts of fat and protein.

This study gives us possible insight into the effect that making small changes to specific dietary components may have on body fat gain.

One point noted by the researchers is fat stimulates the so-called "reward pathways" in the brain, which leads to a strong desire to consume more of it, as seen with addictive substances such as alcohol and cocaine.

It may be the case that the more fat you eat, the more fat you want to eat (at least in mice).

But it's unclear whether these findings would apply to people, or what role physical activity might have in modifying the results.

Current guidelines recommend that:

  • men shouldn't have more than 30g of saturated fat a day
  • women shouldn't have more than 20g of saturated fat a day
  • children should have less

Where did the story come from?

The study was carried out by researchers from the Chinese Academy of Sciences, the University of Aberdeen, the Guangdong Institute of Applied Biological Resources, the University of Dali, and the Center for Excellence in Animal Evolution and Genetics in Beijing.

It was funded by the Chinese Academy of Sciences Strategic Program, the 1000 Talents program, a Wolfson merit award, the National Natural Science Foundation of China, and funds from Guangdong Academy of Sciences.

It was published in the peer-reviewed journal Cell Metabolism.

The UK media covered the details of the research well, but overstated the strength of the conclusions given that this was a study in mice rather than humans.

Also, the Daily Mirror claimed the study provided " 'unequivocal' findings" that fats were solely responsible for weight gain.

But the "fats versus carbs versus sugar" debate has been ongoing for decades, so we doubt this is the last we'll hear about the issue.




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