Many bodybuilders have noticed that it’s easier to burn upper-body fat than lower-body fat. That situation occurs in women and a large percentage of male athletes. Various theories have been proposed to explain the apparent differences between upper- and lower-body fat stores.
In women, lower-body fat acts as an emergency calorie reserve, a precaution designed to ensure perpetuation of the species. Since it takes about 80,000 calories to produce a human baby, nature wants to make sure that expectant mothers get the calories they need, even in times of famine. That’s why women preferentially store fat in their upper thighs, hips and buttocks. Some anthropologists also suggest that female fat storage, especially in the hip and buttocks areas, acts as a sex signal to males, indicating fertility.
Still, that doesn’t explain why many men also have trouble losing fat in their lower bodies. Anyone who’s ever attended a bodybuilding contest has probably noticed male competitors who show razor-sharp muscular definition in the upper body, yet have nary a cut on their legs. Some men ascribe that to ‘localized water retention’ and ‘excessive estrogen secretion.’ While estrogen has potent water-retaining effects and promotes bodyfat accumulation, that’s not the true explanation.
A new study pinpoints the differences in fat mobilization between upper- and lower-body fat.1 Previous studies have measured the appearance of glycerol, which makes up one-third of a triglyceride, or fat, molecule. Trouble is, that’s an indirect measurement and could be inaccurate in regard to the actual speed of the body’s fat use. In the new study British and French scientists teamed to come up with a technique to measure direct fat use, and they applied the newer technique to upper- and lower-body fat release in six lean male subjects aged 22 to 43.
What they found was that gluteal fat tissue shows a 67 percent lower level of blood flow than upper-body fat. It also has an 87 percent lower rate of activity of hormone-sensitive lipase, an enzyme that catalyzes fat release from fat cells, than abdominal-fat cells.
One theory is that the body stores fat in the lower body to protect against high levels of free fatty acids in the blood. A high level of FFAs interferes with glucose uptake in cells, which in turn leads to insulin resistance and diseases linked to insulin resistance, such as diabetes and cardiovascular disease. The body shuttles excess fatty acids directly to lower-body fat stores, where they are ‘locked in,’ which buffers the effect of high levels of fat in the blood.
The fact that lower-body fat may protect against potentially deadly diseases offers little solace to definition-minded bodybuilders. The body won’t use lower-body fat until nearly all upper body fat is oxidized through exercise and diet. So the ultimate answer to eliminating lower-body fat involves persistence and patience. Continuing to exercise and diet will eventually enable you to make progress in getting rid of lower-body fat. For those in a hurry, some evidence shows that using an alpha-2 adrenergic blocker can also enable bodybuilders to tap into lower-body fat stores. The fat cells in the lower body, unlike those in the upper body, have a preponderance of alpha-2 adrenergic cell receptors. (Upper-body fat cells have a preponderance of beta-adrenergic cell receptors, which permit more rapid release of fat.)
One natural alpha-adrenergic blocker is yohimbe at a dose of 0.2 milligrams per kilogram (2.2 pounds) of bodyweight. It must be taken on an empty stomach, however, since any release of insulin totally negates its fat-mobilizing effects.
From a training standpoint, if your goal is increased definition, it may be a good idea to use higher reps, in the range of 15 and up, for lower-body training. Higher reps may increase blood flow, giving you a greater mobilization of lower-body fat.
One other thing to consider is that overtraining the legs can lead to a type of localized stress reaction in which you retain water subcutaneously, or just under the skin, obscuring muscular definition. In their zeal to get more cut, bodybuilders often overtrain their legs prior to a contest, leading to water retention. More experienced bodybuilders often curtail leg training, including aerobics, at least a week before a contest to prevent that effect.
1 Tan, G.D., et al. (2004). Upper and lower body adipose tissue function: A direct comparison of fat mobilization in humans. Obesity Res. 12:114-118.