"Obese people are prematurely old. They have an increased level of inflammation, with higher levels of inflammatory cytokines (small proteins important in cell signalling) in their fat tissue," said Philipp Hohensinner, a researcher at the Medical University of Vienna in Austria.
"Obese people also have shorter telomeres at the end of their chromosomes," Hohensinner said.
Telomeres are the internal clock of each cell. Telomeres get shorter when a cell divides or when oxidative stress causes them to break.
When the telomeres get very short the cell can no longer divide and is replenished or stays in the body as an aged cell.
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The current study investigated whether bariatric surgery and the resulting weight loss could reverse the premature ageing in obese patients.
The study included 76 patients who were 40 years old on average and had body mass index (BMI) of at least 35 kg per square metre (kg/m2). The average BMI was 44.5 kg/m2.
All patients had been unable to lose weight through lifestyle changes and were referred for bariatric surgery. This procedure bypasses the gastrointestinal tract and leaves only a pouch of stomach.
The researchers collected blood samples before surgery and one and two years afterwards. They compared the levels of premature ageing markers in the blood before and after surgery.
One year after surgery BMI had significantly dropped to an average of 27.5 kg/m2, which amounts to a 38 per cent reduction.
Two years after surgery, patients had telomeres that were 80 per cent longer than they had been before the procedure.
"Obesity, and specifically having a lot of fat tissue, seems to put the entire body under increased stress. By losing weight and therefore adipose tissue, that stress reduces, and the body becomes younger," said Hohensinner.
"This is positive news for patients who have bariatric surgery because it shows that the damage from obesity can be reversed," he said.
"Surgery is the last resort for these patients and it is good to see that not only do they lose weight, but they also reduce the stress on their body and reduce the premature ageing," he added.