Dietary fat, not carbs or protein, makes people fat

The study below adds some evidence to the debate that is has been raging for decades – i.e. just what dietary component contributes the most to weight gain. The current favorite “villain” of clinical nutrition are carbohydrates, especially their easily digestible form such as sucrose, fructose, glucose, lactose, etc. The public space is littered with ads admonishing people to watch their carb intake and be especially mindful of the amount of “simple” or added sugars they eat. The rationale is that those carbs lead to an exaggerated insulin response, which medicine claims leads to everything from obesity, to diabetes/cancer/CVD/Alzheimer/etc. While there have also been warnings about consuming too much fat, the warnings have mostly been reframed to vilify saturated fats while essentially giving PUFA (and to a lesser degree MUFA) a free pass. There is plenty of evidence that this advice is approximately opposite to what constitutes a healthy diet, most of the “contrarian” findings never see the light of day in mainstream press. The article below is one of the few exceptions and it was apparently the biggest such study done in more than half a century. It plainly states that indulging in neither carbs nor protein leads to weight gain, while loading up on fat is quite obesogenic. In fact, the relationship was dose-dependent – i.e. the more fat the animals ate, the fatter they became. Since having some fat in the diet is crucial to good health, the study also tried to address the question of how much fat is optimal. The results show that daily fat intake in the 10%-20% range of calories is best when it comes to keeping weight down.

“…Now, new joint research by Chinese and British scientists suggests something simpler – and maybe something we already knew in our gut: to avoid putting on the pounds, avoid fat in your diet. The Chinese government-backed study, published last week in the scientific journal Cell Metabolism, showed that weight gain in mice was linked only to dietary fat levels, not to protein or sucrose. An increased intake of dietary fats was found to drive obesity in mice more than an increase in protein or carbohydrates. In other words, the bigger the proportion of fat in their diet, the more likely they were to overeat, which led to a higher likelihood of obesity. The research involved a collaboration between Chinese and British researchers at the Chinese Academy of Sciences and the University of Aberdeen in Scotland. The study was the biggest nutrition study of its kind in 50 years, according to the team.”

“…The same strictly controlled diets would have been impossible to replicate in testing on humans over the same time period, he said. “We found that the only macronutrient that caused an increase in body fat was dietary fat. So if you ramped up the fat in their diet from 10 to 60 per cent, the mice progressively got fatter and fatter,” Speakman said. An increased amount of fat triggered the release of feel-good hormones like dopamine and serotonin from the brain’s reward centres, making it more pleasurable to overeat, he said. If one’s diet had a relatively low percentage of fat, those reward centres were not activated. The team found that adjusting other macronutrients, like the amount of protein or carbohydrates, had no impact on the weight of the mice.”

“…“Based on our findings, you have to have some fat in your diet since they’re essential for the human metabolism,” he concluded. “We found the mice that gained the least weight were on a diet of 10 to 20 per cent fat – that seems to protect individuals from consuming excess calories.” The typical amount of fat in a standard American diet is 35 per cent, according to a 2006 study.”