Fat cell size and fat loss have an impact on insulin resistance.

Experts have long thought or hypothesized that body fat and in particular abdominal body fat were tied to insulin resistance and increased obesity. Overweight and obese individuals have an increased risk for diabetes and cardiovascular disease so it just makes sense that the cause for weight gain would be tied or related to insulin resistance. One could believe that the amount of weight loss would also result in a decrease in insulin resistance in patients who are predisposed to weight gain and diabetes. To this date, there is limited research to suggest that this is true for obese or overweight individuals.

New research from 2018 indicates a link between adipose size and insulin resistance​[1]​. The research is in the study sought to quantify whether fat cell size and waist circumference loss reduction improve the metabolic risk profile and insulin-resistant individuals and whether this would also correlate with a decrease in insulin resistance itself. This hypothesis makes sense because weight gain around the abdomen would result in increase adipose self size to allow the accumulation of additional body fat.

The researchers performed this study by looking at healthy volunteers who were not obese but had an elevated BMI (overweight). During the study, researchers looked at adipose cell size and multiple metabolic indicators of insulin resistance. They perform the studies both before and after a 14-week hypocaloric diet and two-week weight maintenance plan. The researchers found that a weight loss of 4.3 kg or approximately 9 pounds yielded significant improvements in insulin resistance and many of the metabolic indicators of cardiovascular risk and insulin resistance. The data also indicated that adipose size and waist circumference were linked to insulin sensitivity improvement but the same could not be said for total body weight.

The bottom line: This research indicates that adipose size and waist circumference are tied to improved insulin resistance in overweight adults. In other words, a reduction in insulin resistance directly correlates with a decrease in waist circumference and adipose cell size. This result is likely due to decreased body fat and a reduction in central abdominal fat. I would recommend the people trying to lose weight focusing more on waist circumference than the numbers on the scale.