Health Questions and Answers

Question: What is the immune response to obesity and weight loss?


Obesity appears to be associated with impaired immunity. Overweight patients are at greater risk for infection and bacteremia. Obesity is a risk factor for poor wound healing following surgery. Impaired T-and B-cell function has been noted in comparison to non-obese patients. Obese children and adolescents have impaired delayed-type hypersensitivity, mitogen-stimulated lymphocyte proliferation, and bactericidal capacity of neutophils. However, this general view may not be completely true. One study showed that phagocytosis was not affected by obesity and that the activated monocyte oxidative burst was actually higher among the obese. So while there does appear to be a predisposition to certain infections in the obese subjects, the exact effect on the immune system has not been well defined.

Rapid weight loss and fasting negatively affect immunity. Short term fasting (10-14 days) and weight loss in the obese have have been associated with decrease mitogen-stimulated lymphocyte proliferation. Significant decreases in total leukocytes, neutrophil, monocyte, and NK cell counts, but not T or B cell counts have also been reported following weight loss. Interestingly, these researchers noted seasonal variability of immunity, with decreases seen from January to April.

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