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February 2011

Research Alert: Weight Loss May Reverse Immune System Damage



As a trainer, your job goes beyond merely instructing your clients on proper exercise techniques and weight management. You often have an opportunity to educate clients—especially the severely deconditioned and those with special needs—on the long-term holistic benefits of a healthy lifestyle. In many cases, the information you convey may be potentially life-changing.

Research now suggests that even modest weight loss may reverse many of the damaging changes seen in the immune cells of obese people, particularly those with type 2 diabetes.

One such case is a recent Australian study showing for the first time that even modest weight loss may reverse many of the damaging changes seen in the immune cells of obese people, particularly those with type 2 diabetes.

The study was led by Dr. Alex Viardot and Associate Professor Katherine Samaras from Sydney's Garvan Institute of Medical Research, and published in the Journal of Clinical Endocrinology Metabolism. According to Samaras, the research team used the World Health Organization’s classification for obesity—a BMI between 35 and 50—and that the subjects’ condition ranged from pre-diabetic to having diabetes for five to 10 years. Participants were instructed to follow a diet of 1,000 to 1,600 calories per day for 24 weeks. After 12 weeks, gastric banding (a type of bariatric surgery in which a band is inserted that restricts the size of the opening from the esophagus to the stomach) was performed to further restrict the subjects’ food intake.

Researchers looked specifically at the effects of weight loss on immune cells, and they observed 80 percent reduction of pro-inflammatory T-helper cells, as well as reduced activation of other circulating immune cells (T cells, monocytes and neutrophils) and decreased activation of macrophages (another inflammatory immune cell) in fat. (Before we proceed, a brief synopsis: The immune system is designed to recognize and attack infectious agents. However, on occasion, its recognition apparatus breaks down, and the body begins to manufacture antibodies and T cells directed—or “activated”—against the body’s own cells and organs. This is what occurs in individuals who are obese and/or have diabetes. For more, see sidebar: When Immune System Cells Don’t Work.)

“We also showed that the activation status of immune cells found in fat predicted how much weight people would lose following a calorie-restricted diet and bariatric surgery,” Samaras says. “Those with more activated immune cells lost less weight.”

When Immune System
Cells Don’t Work

According to Dr. Vishwa Deep Dixit, for immune system cells to work properly, they have to be activated at a certain point in time—when they encounter a disease. If they’re activated prematurely or non-specifically—when a person isn’t infected—that person can be predisposed to certain kinds of infections. In obese people, these immune cells are often defective. “If you infect obese animals, they die from influenza a lot quicker than non-obese animals.” 

He explains the connection between obesity and diabetes: “Obese people have a lot of activated immune cells, which produce pro-inflammatory cells called cytokines. These cells make the body resistant to insulin, and the result is the prelude to diabetes.”

Obesity activates the immune system in a negative way by promoting low-grade inflammation throughout the body, possibly causing atherosclerosis and contributing to many other diseases.

Obesity, explains Samaras, activates the immune system in a negative way by promoting low-grade inflammation throughout the body. This inflammation is what causes atherosclerosis and contributes to many other diseases. The more immune cells are activated, the greater their effect on promoting systemic inflammation. When there is an excess of adipose tissue, the cells in fat secrete molecules that promote inflammation. An earlier study Samaras conducted showed a correlation between abdominal fat and inflamed immune cells.

So, what is the difference between a pro-inflammatory immune cell and a beneficial one (the kind that helps the body fight off infection)? “There are times when we need our immune cells to behave in a pro-inflammatory way,” explains Samaras. “For example, when we have a foreign body like a splinter in our finger or when we have a viral or bacterial infection. When we have an excess of fat, our immune system behaves similarly, at a low-grade level.”

Guarded Optimism Over Findings

The reaction to the Australian study in the scientific community, which has known for some time that obese people have a compromised immune system and are more susceptible to infectious diseases, has been one of guarded optimism. Dr. Vishwa Deep Dixit, associate professor at Pennington Biomedical Research Lab in Baton Rouge, La., is intrigued. “I think it’s very interesting work, because it’s one of the first studies in line with the hypothesis that weight loss will reduce inflammation of immune cells. It is still a bit preliminary because next to nothing is known about human immune function and a person’s weight—for example, we don’t know anything about people of normal weight.”

Dixit also says that it is not known if the activated immune cells (T cells, microphages) can produce insulin resistance.

Dr. Janet Rankin, a professor in the department of human nutrition, foods and exercise at Virginia Tech University, found it interesting that the Australian researchers discovered that T-cell production, which had not been examined much vis-à-vis obesity, was substantially correlated with weight loss.

“One difficulty of the study,” Rankin says, “is that they used both energy restriction and gastric banding, so we don’t know which was responsible.”

When asked if she felt that the study’s subjects would have experienced the same benefit without the gastric banding, Samaras replied, “What probably matters more than anything is getting the weight off and keeping it off. The evidence is that for the obese, bariatric surgery of any kind is the only long-term intervention that keeps weight off. Yet if one eats more than necessary after weight loss, they are likely to regain weight, no matter how they lost it.”

“Even in morbidly obese people with advanced, long-term type 2 diabetes who are dependent on insulin, just a modest weight loss of around five pounds has been shown to improve glucose control, blood pressure and blood fat levels.”

Even Minimal Weight Loss Can Be Beneficial

Despite outstanding questions, Samaras emphasizes that the study is very promising, because it demonstrates that there is no point, whether in obesity or type 2 diabetes, beyond which weight loss is futile. “Even in morbidly obese people with advanced, long- term type 2 diabetes who are dependent on insulin, just a modest weight loss of around five pounds has been shown to improve glucose control, blood pressure and blood fat levels.”

These are important findings for your clients, particularly those who are already dealing with the ramifications of being overweight. If your client is obese and/or has type 2 diabetes, and he loses even a modest amount of weight, he can boost his immune system and better manage his diabetes.

As for your clients who aren’t obese, Dixit says, “We have an idea that some exercise is beneficial to their immune system. The question is how it works and which arm of the immune system it affects and which it doesn’t.” Rankin adds that we don’t know whether diet or exercise has more beneficial effects—and if diet, what kind. (Is it low-carbs/high-protein? The reverse?)

In the meantime, as science works at unlocking the secrets of our autoimmune system, fitness professionals should continue to preach the gospel of exercise and proper nutrition—because while we don’t know exactly how they keep us healthy, we know that they do. (See sidebar: Five Workouts a Week Keeps Colds Away.)

Five Workouts a Week Keeps Colds Away

More good news about the benefits of exercise: A study conducted at the Human Performance Laboratories at Appalachian State University in North Carolina and published in the November 2010 edition of the British Medical Journal found that exercise can help you fight colds.

Researchers tracked the respiratory health of 1,000 people, ages 18 to 85, for 12 weeks in fall and winter. They discovered that exercise in the form of a 30-minute power walk at least five times a week activates your immune cells for up to three hours afterward. This helps you fight the harmful pathogens that cause colds. Researchers asked participants questions about their exercise habits and fitness levels. They found that cold symptoms lasted 45 percent less and were less severe in those who worked out five or more times per week.

This research confirmed the findings of two earlier studies:

  • A 2002 study in the journal Medicine & Science in Sports & Exercise found moderate physical activity reduced the risk for an upper respiratory tract infection by 23 percent, compared with low levels of physical activity.
  • A 2006 study in the American Journal of Medicine found one year of a moderate-intensity exercise regimen could reduce the incidence of colds in postmenopausal women who were overweight or obese.



Jim Gerard is an author, journalist, playwright, and stand-up comic. He has written for the New Republic, Travel & Leisure, Maxim, Cosmopolitan, Washington Post, Salon, Details, New York Observer, and many other magazines. For more information, visit his site at




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