Men develop more intraabdominal obesity and signs of the metabolic syndrome after hyperalimentation than women

We prospectively studied the effects of fast food–based hyperalimentation on insulin sensitivity and components of the metabolic syndrome and analyzed this with respect to sex. Twelve nonobese men and 6 nonobese women (26 ± 6.6 years old), and an age-matched control group were recruited. Subjects in the intervention group aimed for 5% to 15% weight increase by doubling their regular caloric intake based on at least 2 fast food meals a day while also adopting a sedentary lifestyle for 4 weeks (<5000 steps a day). Weight of subjects in the intervention group increased from 67.6 ± 9.1 to 74.0 ± 11 kg (P < .001), with no sex difference with regard to this or with respect to changes of total abdominal fat volumes or waist circumferences. Fasting insulin (men: before, 3.8 ± 1.7 μU/mL; after, 7.4 ± 3.1 μU/mL; P = .004; women: before, 4.9 ± 2.3 μU/mL; after, 5.9 ± 2.8 μU/mL; P = .17), systolic blood pressure (men: before, 117 ± 13 mm Hg; after, 127 ± 9.1 mm Hg; P = .002; women: before, 102 ± 5.1 mm Hg; after, 98 ± 5.4 mm Hg; P = .39), serum low-density lipoprotein cholesterol, and apolipoprotein B increased only in the men of the intervention group. The sex differences in the metabolic responses to the intervention were linked to a considerable difference in the fat accumulation pattern; 41.4% ± 9.2% of the increase of the fat volume in the abdominal region was accumulated intraabdominally in men and 22.7 ± 6.5% in women (P < .0001). This study thus showed that women are protected, compared with men, against developing intraabdominal obesity when adopting a standardized obesity-provoking lifestyle. Our findings suggest that it is not different lifestyles and/or behaviors that underlie the fact that men have a higher cardiovascular risk at the same level of percentage of body fat than women.