Eating lots of fatty foods is the only cause of weight gain – not feasting on carbs, research suggests.
Scientists have scratched their heads for years as to whether fat, protein or carbs were the culprit for bulging waistlines.
But ‘unequivocal’ trials on mice pinpoints fat as the problem – and lets commonly-thought offenders such as carbs and protein off the hook.
Mice fed fat-heavy diets consumed the most calories because fat stimulated the reward centres in their brains, scientists found.
Researchers at Aberdeen University and the Chinese Academy of Sciences led the rodent study, considered the largest of its kind.
A drawback in conducting human studies on the effects of diets is time, as most don’t last long enough to draw concrete conclusions.
However, studies on animals that are genetically similar, such as mice, could help point researchers in the right direction.
The professor who led the study, said the new findings offer a ‘good clue’ as to what the different diets may do to humans.
A total of 30 different diets were given to mice over a period of three months – the equivalent of nine human years.
Each varied in their fat, carbohydrate (sugar) and protein content.
The professor said: ‘The result of this enormous study was unequivocal – the only thing that made the mice get fat was eating more fat in their diets.
Mice fed carb-loaded diets, including up to 30 per cent of their calories coming from sugar, gained no significant weight.
And combining sugar with fat no more impact than fat alone, the study revealed.
During the 1980s and 1990s, it was widely accepted that the most important factor in weight gain is the fat content of our diets.
However, in the new millennium it was suggested this focus on fat was misplaced, and the main factor driving obesity was refined carbs.
Most recently,attention has turned to protein, with the hypothesis that people eat food mostly to obtain protein rather than energy.
According to this idea, when the protein content falls, humans eat more to meet the target protein intake – causing them to consume too many calories.