Many athletes and bodybuilders subject themselves to semistarvation diets to lose weight, specifically bodyfat. While such diets, particularly when combined with exercise, are effective in promoting rapid weight loss, much of that loss may not be fat.
A recent study involving an elite branch of the U.S. Army known as the Rangers examined the effect of getting too few calories on physical activity, especially in terms of how hormones interplay in the observed body composition changes.1 Two groups of Army Rangers participating in a rigorous eight-week course. They underwent four repeated cycles of restricted energy intake, followed by refeeding, or an increase in calories. In group 1, 49 Rangers ate diets that averaged between 1,000 and 1,200 calories less than their calculated requirements. After eight weeks most of the men in that group achieved minimal bodyfat levels (none of them started out fat). Measurements of their hormone levels showed that their active thyroid hormone (T3) was below normal, while their testosterone approached castrate levels, meaning that their bodies were hardly making any testosterone. Insulinlike growth factor 1 (IGF-1), another primary anabolic hormone made in the liver under the influence of growth hormone, was only half the normal level. Since IGF-1 is often considered an indicator of growth hormone activity, that likely would also point to a deficient growth hormone release, which makes sense because IGF-1 is acutely sensitive to caloric, particularly protein, intake.
The lack of calories in group 1 also lowered resting insulin levels, which is good for fat loss but not so great for certain hormone levels. For example, the lowered insulin levels led to drops in both active thyroid and testosterone hormones because the normal hormone-binding proteins that extend the activity of the hormones decrease with declining insulin levels.
Cholesterol levels rose significantly in group 1 from an average 158 up to 217. The increase in cholesterol likely resulted from the lowered thyroid activity, since thyroid hormone is known to regulate blood cholesterol levels. Another theory is that people who follow strict diets often show elevated cholesterol levels, as cholesterol is mobilized from degrading fat deposits; however, during the second week of dieting, the soldiers in group 1 showed the beneficial effects of dieting on blood lipids, including higher protective HDL cholesterol coupled with decreased LDL cholesterol, the latter being a risk factor for cardiovascular disease.
Extreme stress frequently correlates to lower testosterone levels, as does lack of sufficient rest and sleep. The Rangers participating in the study certainly were under extreme stress and averaged only 3.6 hours of sleep a day. Despite that, the researchers believe their drop in testosterone levels was more closely related to the lack of calories. They also noted that other stressors, including heat exposure, didn’t appear to adversely affect testosterone levels in people acclimated to such changes.
Cortisol, a catabolic hormone secreted from the adrenal cortex, has an inverse relationship with other anabolic hormones, such as growth hormone, insulin and testosterone. In the study cortisol levels began to rise at the end of the eight-week course, when the men’s bodyfat levels were at their lowest point. The rising cortisol levels were attributed to the need to tap into alternate sources of energy due to the prolonged calorie deficit caused by the diet. The stores most likely to be tapped under such circumstances are muscle, as cortisol promotes amino acids leaving muscle to be degraded into glucose in the liver.
The men in group 2 showed an eight-centimeter loss in upper-arm circumference, an indicator of muscle loss, while those in group 1 showed a 10-centimeter drop in waist measurement. The group-2 subjects, who ate more calories than those in group 1, also avoided both the lowered thyroid effect and the increased blood cholesterol levels that occurred in group 1. Past studies have shown that type 1, or slow-twitch, muscle fibers are preserved better than type 2, or fast-twitch, muscle fibers under energy-deficit conditions. Unfortunately, the type 2 fibers are also more prone to hypertrophy, or muscle size increases, than type 1 fibers.
The authors suggest something long known to many athletes: Supplementing anabolic hormones may halt the catabolic effects of extreme dieting, which in turn may maximize fat losses while preserving muscle. Of course, that doesn’t consider the possible side effects. As an alternative to drug use, the authors also suggest that ‘a useful intervention might include blocking maladaptive responses from catabolic factors that occur in a subset of men losing excessive amounts of fat-free mass.’
I would interpret that enigmatic statement to mean that muscle loss can be controlled through diet and supplements, which might include increased protein intake along with various anticatabolic nutritional elements, such as you would find in complete-milk-protein supplements. IM
1 Friedl, K.E., et al. (2000). Endocrine markers of semistarvation in healthy lean men in a multistressor environment. J Applied Physiology. 88:1820-1830.