They’re the lucky few: people who can eat as much as they like without gaining weight. A new study suggests they can do this because their fat cells burn energy differently – a finding that could lead to new obesity treatments.
Nele Gheldof at the Nestlé Institute of Health Sciences in Switzerland and her colleagues studied 30 men and women who remain very slim – with BMIs of 18.5 or under – despite eating and exercising the same amount as the average person.
By analysing small fat samples sliced from their tummies, the researchers found that the people’s fat cells had abnormally high expressions of genes involved in both breaking down and making fat. Their fat cells were also 40 per cent smaller than those of normal-weight people and contained greater numbers of more active mitochondria – the energy powerhouses of cells.
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The results suggest that naturally slim people are resistant to putting on weight because their fat cells burn lots of energy through what is known as a “futile lipid cycle”, says Gheldof. This means their fat cells are stuck in a constant loop of breaking down and re-building fat molecules – a process that is powered by mitochondria.
The reason why fat cells are smaller in these people may be that the futile lipid cycle only builds up a small amount of fat before breaking it down again, says Gheldof, although further studies are needed to confirm this.
Opposite of obesity
In contrast, obese people often have faulty mitochondria in their fat cells, meaning they can’t burn energy via the futile lipid cycle, says Sihem Boudina at the University of Utah, who wasn’t involved in the study.
Several groups are currently investigating ways to restore mitochondrial activity and kickstart the futile lipid cycle in obese people in the hope of driving weight loss, says Boudina. The recent findings in naturally slim people suggest they are on the right track, she says.
Cold exposure has been shown to activate the futile lipid cycle, which helps explain the trend of wearing ice vests and having ice baths to slim down. But this strategy only works for normal-weight people, not obese people, because obese individuals don’t have the mitochondria machinery that would be needed for this cycle to be initiated in the first place, says Boudina.
American Journal of Clinical Nutrition
