Link between weight loss and immune function

Over half the Australian population is either overweight or obese, with many experiencing corresponding health effects, such as cardiovascular disease and Type 2 diabetes.

Many of these problems are caused by the immune system's response to excess fat. It has been known for some time that excess body fat, particularly abdominal fat, triggers the production of pro-inflammatory immune cells, which circulate in the blood and can damage our bodies.

In addition, other inflammatory immune cells, macrophages, are also activated within fat tissue.

Now Garvan Institute researchers have found that even modest weight loss of only six kilograms can reverse many of the ill effects caused by these immune responses.

The conducted their study on 13 obese individuals suffering from Type 2 diabetes, and placed them on a calorie restricted diet of between 1000 and 1600 calories a day for 24 weeks, along with gastric banding at 12 weeks.

Dr Alex Viardot and Associate Professor Katherine Samaras from Sydney’s Garvan Institute of Medical Research found that modest weight loss as a result of the calorie restricted diet led to an 80 per cent decrease in the number of pro-inflammatory T-helper cells

It also led to reduced activation of other circulating immune cells (T cells, monocytes and neutrophils) and decreased activation of macrophages in fat.

“We have found that a modest weight loss of about six kilograms is enough to bring the pro-inflammatory nature of circulating immune cells back to that found in lean people,” said Associate Professor Samaras.

“These inflammatory cells are involved in promoting coronary artery disease and other illnesses associated with obesity.

“This is the first time it has been shown that modest weight reduction reverses some of the very adverse inflammatory changes we see in obese people with diabetes.”

The researchers suggest that the best way to maintain a high level of health and to stave off disease isn't to take dietary supplements and antioxidants in the hope they'll have anti-inflammatory effects. Simply lower your weight to a healthy level and you'll experience a far greater health impact.

Another interesting finding suggests the activation levels of immune cells found in fat predicted how much weight individuals would lose following the diet, with those having more activated immune cells lost more weight.

“It’s the first time this has been described and is important because it helps us understand why some people lose weight more easily than others, and that inflammation is involved in regulating the response to bariatric surgery,” said Samaras.

The research was published in the Journal of Clinical Endocrinology Metabolism today (doi:10.1210/jc.2009-2371).