A new study now finds that people who are naturally slim may be able to keep their weight down easily because their fat cells are genetically more efficient. The study, published in The American Journal of Clinical Nutrition, saw researchers from Switzerland look at the action of fat cells in a group of men and women who could eat whatever they like without putting on weight.

Notably, according to the story published in Daily Mail, fat cells from their stomach were almost half the size and had more energy to break fat down than those in people of average weight. The finding also adds to the belief that thin people have some genetic advantage when it comes to maintaining their figure.

The study authors wrote that the study, a world-first, showed that persistent low body weight in humans is associated with features in the white adipose tissue that are opposite to those of obese patients.

The team from Switzerland looked at white adipose tissue, which is the main form of fat in the body and store lipids.

The team at the Nestlé Institute of Health Sciences, studied 30 men and women who remain very slim and had a BMIs of 18.5 or lower. The study authors noted that these people did not have distorted eating patterns and ate and exercised like any other normal human being.

The participants had a small amount of fat sliced from their stomach to be analysed, and also gave blood, urine and stool samples for the test.

The researchers found that slim people's fat cells had abnormally high expressions of genes involved in both breaking down and making fat and that their fat cells were 40 percent smaller than those of normal weight people. The results from the study also showed that slim people's fat cells had more active mitochondria, a part of a cell which uses energy to help the cell break down and renew itself. Since the mitochondria in slim people work at a higher level, the fat cells are breaking down and re-building molecules more efficiently.

Terming it 'futile lipid cycle', it could explain why people are resistant to weight gain, according to study authors slim.

Turns out, their fat cells are genetically inclined to burn so much fat for energy to break down and rebuild other fat cells, that they never get enough time to accumulate enough to allow a person to put on some weight.