Influence of Obesity on Immune Function

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Abstract

Objective To compare immune function in obese and nonobese subjects.

Design Obese and nonobese subjects were compared cross-sectionally. To test for the influence of other factors on immunity, aerobic fitness, psychological well-being, and serum levels of glucose, triglycerides, and cholesterol were measured and included in multiple regression models to determine their comparative effects.

Subjects/setting Community-based subjects included 116 obese women (age=44.3±9.7 years, body mass index= 33.2±6.5) and 41 nonobese women (age=42.2±10.9 years, body mass index=2 0.2±1.9). Statistical analyses performed Independent t tests, Pearson product moment correlations, and step wise multiple regression procedures.

Results Obesity was linked to elevated leukocyte and lymphocyte subset counts (except for natural killer and cytotoxic/suppressor T cells), suppressed mitogen-induced lymphocyte proliferation (an index of T- and B-cell function), higher monocyte and granulocyte phagocytosis and oxidative burst activity, and normal activity of natural killer cells.

Applications/conclusions These data support the contention that obesity is associated with alterations in immune function. Further research is needed to link immunosuppression with the previously reported elevated risk of infection among the obese. J Am Diet Assoc. 1999;99:294-299.

Section snippets

Subjects and Research Design

Obese and nonobese, female, white subjects were recruited from the surrounding community through advertisements according to these selection criteria (14): between the ages of 25 and 75 years; in good health with no known diseases, including diabetes, cancer, and heart disease; body mass index (BMI, calculated as kg/m2) between 25 and 65 for obese subjects and less than 25 for nonobese subjects (20); not currently following a reducing diet; not using medications known to affect immune function;

Results

The obese and nonobese groups were of similar age and height (Table 1). Compared with nonobese subjects, obese subjects had a 54% greater body mass, nearly twice the body fat percentage, and a 43% lower Vo2max. Serum cholesterol, triglycerides, and glucose levels were each significantly higher among obese subjects than nonobese subjects (but none of the subjects had a fasting glucose value indicating diabetes mellitus). Psychological general well-being was significantly lower among the obese

Discussion

Data from this study indicate that obesity is related to elevated leukocyte and lymphocyte subset counts (except for natural killer and cytotoxic/suppressor T cells), lower T- and B-cell function, higher monocyte and granulocyte phagocytosis and oxidative burst activity, and normal activity of natural killer cells.

Limited published data exist comparing immunity in obese and nonobese subjects (2), (11), (12), (13), (14). Our finding that the obese subjects (all nonsmokers) had higher total

Applications

In this cross-sectional study, obesity was associated with alterations in various measures of immune function. Granulocyte and monocyte activity was chronically elevated in obese subjects. This may be of concern because these cells can release potentially damaging substances, such as free radicals and proteolytic enzymes, which promote atherosclerosis. T-cell function was suppressed in 19% to 32% of the obese subjects (depending on the mitogen used), whereas the function of natural killer cells

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