The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 13 No. 6 • December 2010


Overfeeding and Regional Effects on Fat Cells

Upper Body Subcutaneous (sc) Fat Cells Differently Affected by Overeating Than Lower Body sc Fat Cells

A new study1 reports on the effects of overeating on subcutaneous fat cells located in the upper body compared to those in the lower body. Though the study examined only subcutaneous (not visceral) fat cells in both regions, the effects of overeating differed substantially between them.

As the paper notes, fat cells can respond to extra nutrients (overfeeding) by either increasing fat-cell numbers (by creating more fat cells) or increasing the size of already existing fat cells (hypertrophy). The difference is important because newly created fat cells are small and are relatively insulin sensitive as compared to big fat cells. The results showed that on average, the size but not the number of abdominal subcutaneous adipocytes increased significantly in response to fat gain (p=0.001). The change in abdominal subcutaneous adipocyte size was related negatively to baseline size in women but not in men. That is, the women who started with smaller abdominal subcutaneous fat cells gained abdominal fat largely via adipocyte hypertrophy, whereas women with an average adipocyte size “must have” recruited new, smaller adipocytes since the average size of mature adipocytes decreased. “Virtually all men increased abdominal adipocyte size irrespective of baseline size.”1

On the other hand, femoral (leg) subcutaneous adipocyte size remained unchanged in the face of increased leg fat, where overfeeding resulted in a significant increase in lower-body adipocyte number. For both men and women, however, smaller femoral adipocytes increased the average size of mature adipocytes, whereas average adipocyte size decreased in men with femoral adipocytes larger than ~0.35 μg lipid per cell and in women with femoral adipocytes larger than ~0.75 μg lipid per cell.” In the study as a whole, ‘we confirmed that the relative fat gain in the lower body is a strong negative predictor of the change in abdominal subcutaneous adipocyte size.”1

This study helps a great deal in explaining the relative health implications of fat gain in lower body fat cells as compared to fat gain in upper body fat cells, where upper body fat cells (more likely to be larger and less insulin sensitive) are more closely linked to metabolic abnormalities such as diabetes. It also disproves the belief that the number of fat cells is relatively fixed in adulthood by showing that fat cells can not only increase in size in response to overfeeding but also their numbers can be increased.*

Additional research on the differences in signal transduction within upper body subcutaneous fat cells versus lower body subcutaneous fat cells might reveal a way of making the upper body sc fat cells function more like lower body sc fat cells, thereby reducing the health risks associated with upper body sc fat cells.


* “Using a longitudinal intervention model to study increases in body fat caused by overfeeding normal-weight adults, we found that gain of only ~1.6 kg. of lower-body fat resulted in the creation of ~2.6 billion new adipocytes within 8 wk.”


Reference

  1. Tchoukalova et al. Regional differences in cellular mechanisms of adipose tissue gain with overfeeding. Proc Nat Acad Sci USA, 107(42):18226-31 (2010).

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