This study shows that although the waistline may get smaller with dieting alone, it takes physical activity as well to reduce the size of the subcutaneous fat cells that effect type 2 diabetes. Previous studies have shown that large subcutaneous abdominal fat cells are likely to cause diabetes – independently of how obese or overweight the patient may be.
In the current study by Tongjian et al, 45 obese, middle-age women (average age: 58) were randomized to one of three groups. The first group was put on a diet to reduce their energy intake by 2,800 calories per week. The second group was put on a diet plus a regimen of treadmill walking at a moderate pace (one to two miles per hour) three times weekly. The third group was put on a diet plus more-intense exercise (three to four miles per hour on a treadmill) three times a week. In the two exercise groups, the combination of dieting plus exercise was designed to achieve a weekly energy deficit of 2,800 calories.
At 20 weeks, all three groups had lost a comparable amount of weight. The diet-only group averaged a 10.4 kg loss, the diet plus moderate exercise group 10.9 kg, and the diet plus intense exercise group 8.8 kg. The latter group maintained more lean tissue and therefore lost slightly less weight. All groups reduced their waist size by a similar amount. The diet only group slimmed by an average of 8.8 cm, the diet plus moderate exercise group 9.4 cm, and the diet plus intense exercise group 9.3 cm.
Analysis of biopsied subcutaneous abdominal fat cells, however, revealed that while the cells of the diet-only group shrank by an average of 0.8%, those of the moderate exercise group shrank by about 18% and those of the intense exercise group by nearly 17% compared with the diet group. There was no significant difference between the exercise groups.
These findings are consistent with previous research suggesting that exercise preferentially mobilizes fats from the abdominal region as opposed to other areas of the body. The weight loss and waist reduction in the diet-only group probably resulted from shrinking visceral and intramuscular fat cells in the abdomen, rather than subcutaneous abdominal fat cells, although the study did not directly examine these others types of fat cells.
Comment
This study is consistent with other studies which have examined the importance of physical activity in the prevention of type 2 diabetes. Physical activity reduces the size of the subcutaneous abdominal fat cells and it is this which reduces the risk of diabetes. These findings confirm the importance of regular physical activity, not merely in achieving a slimmer waist, but in the prevention of diseases known to be associated with overweight and obesity.
Tongjian You et al. Addition of aerobic exercise to dietary weight loss preferentially reduces abdominal adipocyte size. International Journal of Obesity 2006; 30:1211-1216.
