A plethora of solutions promising spot reduction have been offered to consumers, ranging from potions and unguents to vibrating belts, to subdermal injections, to surgical liposculpture.3-5 Though the surgical techniques are highly effective (and expensive) and mesotherapy is gaining support as practitioners gain experience and expertise, the nonmedical approaches have generally been disappointing. Several sprays and creams have claimed success in limited clinical trials, but most of these products have been debunked by consumer advocates or in the court of public opinion.6

Studies on Subcutaneous Fat
    A new study accepted for publication by the American Journal of Physiology— Endocrinology and Metabolism presents evidence that exercise may offer local benefit in fat loss.7 That’s right. Pumping up the biceps may shred the overlying fat as it’s stimulating the muscle to grow…kinda. Some studies and reports have suggested that weight training may cause quicker fat loss from the overlying area or at least create a leaner appearance, while others refute the claim, though the research is very limited and most of it is dated. For example, two studies performed in the 1960s had subjects exercise one arm for a period of time and measured the change in skinfold thickness, comparing the exercised arm to the control arm of each individual. One study demonstrated a significant decrease in subcutaneous fat (the kind you can pinch) over the exercised arm only, while the other study showed a significant decrease in subcutaneous fat over both arms.8,9

    The findings of the second study reporting fat loss over both arms is more consistent with observations made in athletes who emphasize one-sided movements.9 A more recent study, published in 1971 (yes, that was sarcasm) measured skinfold thickness of the arms of tennis players and control subjects (nonathletes).10 Though tennis players tend to develop the muscles of their dominant arm and shoulder due to the (typically) one-handed grip on the racket, there was no difference in skinfold thickness between the dominant and non-dominant arms. Tennis players were significantly leaner than the control subjects, but that was to be expected.10
    Another study including 10 women had the subjects exercise one leg only for five weeks. Though the exercised leg demonstrated a slight decrease in subcutaneous fat thickness and the control leg that did no exercise showed a slight gain in subcutaneous fat, the differences were not significant, possibly due to the small number of people in the study.11

A Leg Up
    Given the contradictory findings and lack of recent investigations, the submission of a well-designed study by a group of Danish scientists from the University of Copenhagen, Denmark, is a welcome addition to the literature.

    This group took a step back and designed an experiment to prove that during exercise, more fat is released from fat cells overlying the exercising muscles than other (sedentary) areas. They endeavored to prove that there’s an increase in the breakdown and release of stored fat and greater blood flow to disperse the newly freed fatty acids over the quadriceps of an exercised leg as compared to the opposite leg, which was not exercised. Needle-like catheters were inserted into both legs to measure the blood flow and breakdown of stored fat in the subcutaneous fat overlying the exercised or sedentary quadriceps muscles. Another catheter was inserted into an artery of the arm to measure epinephrine (adrenalin) and insulin, the two hormones most affecting fat storage and release, as well as comparing general (whole body) stored fat breakdown to the breakdown occurring over the muscles. Finally, a mask was placed over the mouth and nose that could measure the relative amount of effort (work) being performed.

    The 10 subjects, all healthy young men, fasted overnight and avoided smoking or any beverages that might affect the results (alcohol, caffeine, nicotine) for 12 hours prior to exercise. At this point, the experiment began using an exercise protocol completely unlike the weight training used to build muscle, limiting the applicability of the findings for a strength athlete. The subjects performed three hours of leg extensions (with two breaks of 30 minutes each) at varying intensities, to see what effect the exercise had on the overlying adipose tissue. One aspect of the study design that seemed a bit flawed was that one leg was exercised at two different intensities during the session for one hour total, while the other was exercised at only one intensity, but for two hours total. One would assume that the ongoing exercise in the opposite legs would keep the general (whole body) sympathetic tone (adrenalin levels) and lipolysis (fat breakdown) elevated, making it more difficult to detect local differences as the study progressed.

    Regardless, the researchers detected some notable differences between the exercised leg and the sedentary leg. A greater blood flow was noted in the fat tissue overlying the exercised leg at the lower two intensities. Surprisingly, the highest intensity (85 percent Wmax [maximum work capacity]) failed to show any difference, possibly due to the interfering factors present in the opposite leg, which had recently completed 120 minutes of knee extensions at 55 percent Wmax. A more ideal study design would have used three different groups and compared the different intensities over the same amount of time. One of the factors determining local blood flow is heat generation, as the body adapts to overheating by allowing more blood to flow through the skin and underlying fat tissue. It’s possible that while 30 minutes may have been sufficient recovery time after a 30-minute, 25 percent Wmax session, it doesn’t appear to have been enough after the 120-minute, 55 percent Wmax session.