Basically, the two ratty cohorts were fed more than sufficient, except one group was supplemented with arginine and the other alanine (another amino acid) as a control. The rats fed arginine put on far less weight than the controls.

They also concluded that supplementation with arginine shifts nutrient partitioning to promote skeletal-muscle gain.

It’s not really clear how the amounts given to the rats translate to a human-sized dose, nor is it clear as to the mechanism whereby arginine does this, but to my reckoning it might have something to do with this: “Arginine stimulates growth hormone secretion by suppressing endogenous somatostatin secretion“.

Regardless, given that I hate hate hate fat, I might just buy a tub next time I’m at the shop and see if it does anything besides:

• Acting as a precursor for the synthesis of nitric oxide (NO)
• Improving immune function
• Reducing healing time of injuries (particularly bone)
• Quickening repair time of damaged tissue
• Reducing risk of heart disease
• Helping to improve insulin sensitivity
• Helping to decrease blood pressure
• Alleviating male infertility, improving sperm production and motility
• Increasing circulation throughout the body, including the sex organs

Even if only the last one comes true, I think it’ll be worth the price!!

Here’s the abstract:

Dietary L-arginine supplementation reduces white fat gain and enhances skeletal muscle and brown fat masses in diet-induced obese rats.

J Nutr. 2009 Feb;139(2):230-7. Epub 2008 Dec 23. PMID: 19106310

Previous studies showed that dietary L-arginine supplementation decreased white fat mass in genetically obese rats. This study tested the effectiveness of L-arginine in diet-induced obesity. Male Sprague-Dawley rats were fed for 15 wk a high-fat (HF) (40% energy) or low-fat (LF) (10% energy) diet beginning at 4 wk of age, resulting in 18% higher body weight gains and 74% higher weights of major white fat pads (retroperitoneal, epididymal, subcutaneous, and mesenteric adipose tissues) in HF than in LF fed rats. Starting at 19 wk of age, rats in each dietary group were supplemented for 12 wk with 1.51% L-arginine-HCl or 2.55% L-alanine (isonitrogenous control) (n = 8 per treatment) in drinking water and arginine groups were individually pair-fed to alanine controls. Despite similar energy intake, absolute weights of white fat pads increased by 98% in control rats over a 12-wk period but only by 35% in arginine-supplemented rats. The arginine treatment reduced the relative weights of white fat pads by 30% and enhanced those of soleus muscle by 13%, extensor digitorum longus muscle by 11%, and brown fat by 34% compared with control rats. Serum concentrations of insulin, adiponectin, growth hormone, corticosterone, triiodothyronine, and thyroxine did not differ between control and arginine-supplemented rats. However, arginine treatment resulted in lower serum concentrations of leptin, glucose, triglycerides, urea, glutamine, and branched-chain amino acids, higher serum concentrations of nitric-oxide metabolites, and improvement in glucose tolerance. Thus, dietary arginine supplementation shifts nutrient partitioning to promote muscle over fat gain and may provide a useful treatment for improving the metabolic profile and reducing body white fat in diet-induced obese rats.