In 1998, Weinstock, et. al., conducted study about the pursuit of combating obesity, short-term studies have demonstrated the positive effects of both diet and exercise on insulin sensitivity. This study aimed to investigate the outcomes of a 48-week supervised diet and exercise program on weight and insulin sensitivity among obese women, specifically focusing on the phases of initial weight loss, maintenance, and subsequent weight regain over a 96-week period.

Forty-five obese women were randomly assigned to one of three treatment groups: (1) diet alone, (2) diet combined with aerobic training, and (3) diet combined with strength training. All participants underwent the same 48-week group behavior modification program and adhered to a prescribed diet. Exercise sessions were supervised three times per week for the first 28 weeks and reduced to two sessions weekly until week 48. Participants were unsupervised during weeks 48 to 96. Oral glucose tolerance tests were conducted at baseline and weeks 16, 24, 44, and 96.

All three groups achieved a mean weight loss of 13.8 kg by week 16, leading to a significant reduction in insulin levels (61.8% of baseline). No significant differences were observed among the groups in terms of changes in body mass index, weight, glucose tolerance, or insulin levels at weeks 16, 24, and 44. Interestingly, neither aerobic nor strength exercise demonstrated an additional beneficial effect on insulin resistance, as measured by serum insulin levels before and after a glucose load. At week 96, the 22 subjects who were studied maintained a loss of approximately 10% of their initial weight. However, insulin levels had returned to pretreatment levels, despite only partial weight regain.

This study reaffirms the positive impact of weight reduction on hyperinsulinemia in obese individuals. Surprisingly, participation in supervised exercise did not yield additional improvements in weight loss or insulin sensitivity. Notably, there was a marked increase in insulin levels even with partial weight regain. The findings underscore the need for further investigation to determine the sustained weight loss required for continued enhancement of insulin sensitivity in individuals struggling with obesity.

Reference: Weinstock, R. S., Dai, H., & Wadden, T. A. (1998). Diet and exercise in the treatment of obesity: effects of 3 interventions on insulin resistance. Archives of internal medicine, 158(22), 2477-2483.