Thigh circumference and risk of heart disease and premature death: prospective cohort study

The paper by Heitmann and Frederiksen1 provides a valuable
contribution in understanding the role of fat free mass and muscle mass on
health. According to their findings a low thigh circumference was
associated with an increased risk of developing heart disease or premature
health. As the authors state “The adverse effects of small thighs might be
related to too little muscle mass in the region”. The authors can only
speculate on the possible mechanism that explain the role of increased
muscle mass on decreased risk of mortality.

In one of our studies (Nassis et al., 2005) body composition was
determined with DXA and insulin sensitivity with oral glucose tolerance
test before and after 12 weeks of aerobic training in 19 overweight and
obese girls aged 9-15 years. In addition, adiponectin, CRP, IL-6, IGF-1,
sICAM-1 and sVCAM-1, blood lipids and lipoproteins concentration was
determined pre- and post-training. The major finding was a 23.3%
improvement in insulin sensitivity as shown by the smaller (compared with
pre-training levels) area under the insulin concentration curve (AUC)
after training (12781.7±7454.2 vs. 9799.0±4918.6 ìU•min/ml, before and
after intervention, respectively, P= 0.03). Insulin sensitivity was
improved in these girls without changes in body weight, percent body fat,
waist circumference and estimated visceral fat. Lower limb fat free mass
(LLFFM) increased by 6.2% (P<0.01), as a result of training. The
interesting finding was that LLFFM increase was inversely correlated with
lowering of insulin AUC (r= -0.68, P<0.01). Finally, this improvement
in insulin sensitivity was without change in serum adiponectin, IL-6 and
CRP concentrations.

These findings are in agreement with other studies in adults, which
suggest that exercise training-induced improvements in insulin sensitivity
with no change in total body and visceral fat may be due to changes in the
ability of muscles to metabolize glucose3. The increase in the LLFFM in
our study2 is in accordance with this concept.

Since skeletal muscle is the primary target tissue for insulin
action, it is tempting to suggest that the observed exercise training-
induced increase in muscle mass may, at least in part, explain the
enhanced insulin sensitivity in these studies. Conclusively, there is
evidence in the literature that exercise induced increase in fat free mass
of the legs might contribute to improved health risk factors such as
insulin resistance. This exercise-induced effect might, at least
partially, explain the lower risk for cardiovascular disease with
increased thigh circumference in Heitmann and Frederiksen’s 1 study.

George P Nassis1 and Labros S Sidossis2

1Department of Sport Medicine and Biology of Physical Activity,
Faculty of Physical Education and Sport Science, National and Kapodistrian
University of Athens, Greece

2Laboratory of Nutrition and Clinical Dietetics, Department of Nutrition
and Dietetics, Harokopio University, Athens, Greece

References

1. Heitmann BL and Frederiksen P. Thigh circumference and risk of
heart disease and premature death: prospective cohort study. BMJ 2009;339:
b3292

2. Nassis GP, Papantakou K, Skenderi K, Triandafillopoulou M,
Kavouras SA, Yannakoulia M, Chrousos GP, and Sidossis LS. Aerobic exercise
training improves insulin sensitivity without changes in body weight, body
fat, adiponectin and inflammatory markers in overweight and obese girls.
Metabolism 2005;54:1472-1479

3. Potteiger JA, Jacobsen DJ, Donnelly JE and Hill JO. Glucose and
insulin responses following 16 months of exercise training in overweight
adults: the Midwest Exercise Trial. Metabolism 2003;52:1175-1181

Competing interests:
None declared