Slim people have ‘smaller fat cells with more energy’, scientists find
Naturally slim people stay that way ‘because their fat cells are smaller and more active’ even if they eat too much or don’t exercise
- Scientists analysed the bodies of people who eat normal amounts but are thin
- They found their stomach fat contained cells which were smaller
- Their cells contained more of the energy busting component mitochondria
People who are naturally slim may be able to keep their weight down effortlessly because their fat cells are genetically more efficient, a study has suggested.
Scientists looked at the action of fat cells in a group of men and women who could eat whatever they liked without putting on weight.
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 findings add to the belief that thin people have some genetic advantages when it comes to maintaining their figure.
Slim people may keep their low weight because they have smaller fat cells with more energy, according to scientists from Switzerland (stock image)
Writing in The American Journal of Clinical Nutrition, the researchers, from Switzerland, said they believe their findings are a world-first.
They said: ‘We show for the first time, to our knowledge, that persistent low body weight in humans is associated with features in the white adipose tissue that are opposite to that of obese patients.’
The team looked at white adipose tissue, which is the main form of fat in the body. They store lipids, which are fatty substances from the foods in our diet.
Obesity rates have soared by three-fold since 1975.
But the trends are the same in people both with and without what are known as ‘fat genes’, according to a study published in the BMJ in June.
This suggests poor diet and lack of exercise – poor lifestyle choices – are mainly to blame, researchers said.
Scientists based in Norway looked at findings, including BMI measurements, from a previous study of 118,959 adults who had repeated height and weight measurements recorded between 1963 and 2008.
Participants were divided into five groups depending on their genetic risk to obesity, a fifth being the most susceptible and a fifth being the least.
People in the top ‘genetic-susceptibility’ group were more likely to have a higher BMI than those identified as having a lower risk, it found.
But the findings also showed BMI has increased for both genetically predisposed and non-predisposed people since the 1960s.
Lead author Maria Brandkvist, a PhD student, said: ‘Genetically predisposed people are at greater risk for higher BMI and that genetic predisposition interacts with the obesogenic environment resulting in higher BMI.
‘An altered dietary pattern is the most plausible environmental factor influencing excess energy balance.
‘However, a more sedentary lifestyle and possibly changes in the biological environment, such as toxins and microbiota, could also contribute.’
The team at the Nestlé Institute of Health Sciences, studied 30 men and women who remain very slim.
They had a BMIs of 18.5 or lower, which would be considered underweight by the NHS.
The authors noted that these people did not have disordered eating patterns and ate and exercised a normal amount.
The participants had a small amount of fat sliced from their stomach to be analysed, and also gave blood, urine and stool samples.
The researchers found that the slim people’s fat cells had abnormally high expressions of genes involved in both breaking down and making fat.
More than 200 gene variations influence weight, such as fat distribution and metabolism.
The slim people’s fat cells were 40 per cent smaller than those of normal weight people.
Fat tissue with fewer but larger cells is described as ‘hypertrophic’, whereas fat tissue with lots of smaller sized cells is ‘hyperplastic’.
Fat tissue in a hypertrophic state is linked with insulin resistance, diabetes and cardiovascular disease such as heart disease.
The results also showed the 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.
Because the mitochondria are working at a higher level, the fat cells are breaking down and re-building molecules more efficiently.
The researchers called the process a ‘futile lipid cycle’, and could explain why slim people are resistant to weight-gain, the authors said.
Effectively, their fat cells are genetically inclined to burn so much fat for energy to break down and rebuild other fat cells that they never have time to accumulate enough for someone to put on weight.
The cycle of constantly burning fat down may also explain why fat cells are smaller in slim people, Dr Gheldof and colleagues wrote.
The findings could ultimately create new avenues for weight loss treatments.
Millions of people worldwide are at risk of heart disease, stroke, type 2 diabetes and cancer due to being overweight.
In the UK alone, one in four adults are obese.
It’s previously been discovered that obese people have faulty mitochondria in their fat cells, meaning they can’t burn fat as well.
This can also lead to metabolic conditions, the authors said, which include diabetes.
The stools of the slim participants did not show any differences, however, they did have lower levels of creatine, a waste product from the body, in their urine.
This could also explain why they have less muscle mass, due to low creatinine levels normally being a sign of losing muscle mass as people age.
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