Obesity is a widespread health concern with significant implications for overall well-being. Dietary restriction, a common approach to managing obesity, often faces challenges such as poor adherence, protein breakdown, and slow progress in weight reduction. Growth hormone (GH) plays a crucial role in regulating metabolism, and its potential to accelerate lipolysis (fat breakdown) has garnered attention. This article explores the effectiveness of GH treatment, specifically recombinant human GH, in promoting weight loss, preserving lean body mass, and improving metabolic parameters in obese individuals undergoing dietary restriction.
The Role of Growth Hormone in Lipolysis and Anabolism
Growth hormone (GH) can induce an accelerated lipolysis. Impaired secretion of GH in obesity results in the consequent loss of the lipolytic effect of GH. GH also exerts an anabolic effect by increasing insulin-like growth factor-I (IGF-I), which promotes muscle growth and protein synthesis. These dual actions of GH make it a potential therapeutic agent for combating obesity and its associated metabolic complications.
Study Design and Methodology
To investigate the effects of GH treatment and dietary restriction on lipolytic and anabolic actions, as well as the consequent changes in insulin and GH secretion in obesity, a randomized, double-blind, placebo-controlled trial was conducted. The study involved 24 obese subjects (22 women and 2 men, aged 22-46 years). Participants were placed on a hypocaloric diet consisting of 25 kcal/kg ideal body weight (IBW) with 1.2 g protein/kg IBW daily. They were then randomly assigned to receive either recombinant human GH (n = 12, 0.18 U/kg IBW/week) or a placebo (n = 12, vehicle injection) for a duration of 12 weeks. This rigorous study design ensured that the results were reliable and unbiased.
Key Findings
The study revealed several significant findings regarding the effectiveness of GH treatment in obese individuals:
Enhanced Fat Loss
GH treatment caused a 1.6-fold increase in the fraction of body weight lost as fat and a greater loss of visceral fat area than placebo treatment (35.3 vs. 28.5%, p < 0.05). This indicates that GH effectively promotes fat breakdown and reduces the accumulation of visceral fat, which is associated with increased health risks.
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Preservation of Lean Body Mass
In the placebo group, there was a loss in lean body mass (-2.62 +/- 1.51 kg) and a negative nitrogen balance (-4.52 +/- 3.51 g/day). By contrast, the GH group increased in lean body mass (1.13 +/- 1.04 kg) and had a positive nitrogen balance (1.81 +/- 2.06 g/day). This demonstrates that GH treatment helps preserve and even increase lean body mass during dietary restriction, which is crucial for maintaining metabolic function and overall health.
Increased IGF-I Levels
GH injections caused a 1.6-fold increase in IGF-I, despite caloric restriction. This confirms that GH effectively stimulates the production of IGF-I, which is essential for its anabolic effects.
Improved GH Secretion
GH response to L-dopa stimulation was blunted in all subjects and it was increased after treatment in both groups. This suggests that GH treatment may help restore normal GH secretion patterns in obese individuals.
Reduced Free Fatty Acid Levels
GH treatment did not induce a further increase in insulin levels during an oral glucose tolerance test (OGTT) but significantly decreased free fatty acid (FFA) levels during OGTT. The decrease in FFA area under the curve during OGTT was positively correlated with visceral fat loss. This indicates that GH improves insulin sensitivity and reduces the availability of FFAs, which can contribute to insulin resistance and metabolic dysfunction.
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