Background:
As the epidemic of obesity in the United States steadily worsens, black women are disproportionately affected. Diminished insulin sensitivity has been linked with obesity and heightened risk of subsequent type 2 diabetes (T2D) and cardiovascular disease (CVD).
Hypothesis:
We propose that a decrease in fat mass achievable by weight loss intervention at the worksite improves insulin sensitivity in overweight black women.
Methods:
Fifty-four overweight black women [age 45±10 years (mean±SD), BMI range 25.9 to 54.7 kg/m
2
] completed a 6-month program that included web-based nutrition information and/or dietitian counseling and access to exercise rooms near their work areas. All participants were advised to reduce daily caloric intake by 500 kcal and instructed to increase daily activity by 5,000 steps, measured by pedometer, above baseline readings. The following measurements were performed: weight, total fat mass by dual-energy X-ray absorptiometry, and insulin sensitivity index (S
I
) calculated from the minimal model. Repeat of all measurements was performed at 6 months.
Results:
Baseline S
I
(median 3.0 liter/mU
-1
•min
-1
, range 0.74 to 7.58 liter/mU
-1
•min
-1
, with lower values signifying insulin resistance) was negatively associated with fat mass (r= -0.584, P<0.001) independent of age. Significant reductions in weight (92.6±18.1 to 91.1±18.9 kg, P<0.01) and fat mass (40.8±12.4 to 39.4±12.6 kg, P<0.01) were determined for subjects completing the program. Reduction in fat mass following completion of the program was associated with an increase in S
I
(r= -0.293, P=0.032). When analyzed by tertiles of fat mass change (Figure), compared to the tertile with net fat mass gain (far left bar), the two tertiles with net fat mass loss had significantly improved insulin sensitivity (higher S
I
).
Conclusions:
Even modest fat mass reduction in overweight non-diabetic black women with a combination of diet and exercise can improve insulin sensitivity, which has the potential to reduce or delay the onset of T2D and CVD.
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