Weakness in immune system can make it harder to lose weight
Weaknesses in our immune system - normally linked to fighting infection and disease - have now been linked to our failure to lose weight.
New research by a team of Irish, American and Canadian researchers suggests problems in the immune system could be responsible up to 40pc of our body's ability to regulate weight.
Obesity expert Prof Donal O'Shea, who is one of the study's lead authors, said: "We know that once weight is gained, for the majority of people it is very difficult to lose that weight.
"It is too simplistic to say eat less, move more and the weight will come off. It doesn't actually work like that. The body has a very powerful reaction to defend against weight loss, which we now know involves the immune system.
"We normally think of the immune system as something that guards against infection and diseases. However, in evolutionary terms, a sudden or rapid weight loss could be a more immediate threat to survival.
"This immune system response contributes to why people really struggle to lose weight, despite their best efforts to control calories and do exercise. Our findings give us a much better understanding of why this is so and they illustrate the dynamic role that the immune system plays in regulating body weight."
Chief author, Lydia Lynch of Harvard Medical School and TCD, said: "We discovered that a very common immune cell, called the invariant natural killer T cell (iNKT cell), often described as the Swiss army knife of the immune system because it does so many jobs, plays a key role in setting off a complex chain of events that regulate and enhance weight loss.
"It is needed to help fat cells make a small protein which triggers the body to metabolise or turn white fat into a much healthier brown fat."
This browning of white fat uses large amounts of energy, leading to increased metabolic rate and weight loss, the findings in the journal 'Cell Metabolism' revealed.
Dublin fitness instructor Brendan Quinn became obese, although he had not altered his diet and exercise levels.
His weight went from 76kg to 120kg over three years.
Prof O'Shea treated him for his immune system and this allowed him to lose weight.
"The results were almost immediate. I lost 12kg in the first five weeks and a total of 23kg since I started treatment five months ago," he said.
Prof O'Shea said the findings should help break many of the stigmas associated with obesity, and most importantly, they could dramatically improve outcomes. It underlines the absolute importance of prevention of weight gain.