The answer is a bit hazy, and that’s not the booze talking. “Based on the available research, the body’s response to alcohol ingestion is definitely dose-dependent,” says Layne Norton, nutritional sciences PhD, natural professional bodybuilder and founder of BioLayne.com. “While higher levels of alcohol intake (three to four drinks for an average-size male) can reduce insulin sensitivity and glucose tolerance — both of which negatively affect fat loss — a small amount (about one drink) can even enhance insulin sensitivity.” This may explain, at least in part, why epidemiological studies have demonstrated that women who regularly drink small amounts of alcohol are leaner than those who do not drink at all, despite a higher caloric intake.
Before you fill ’er up, however, keep in mind this is just a correlation, not necessarily causation. It’s much clearer that consuming large amounts of alcohol inhibits fat burning and is highly associated with obesity and insulin resistance.
“Furthermore, consuming alcohol in large amounts before exercise reduces strength and endurance, while consuming a large amount after exercise impedes recovery and power output in subsequent exercise sessions,” Norton says. “Acute and chronic alcohol ingestion in large amounts also significantly drops testosterone levels, which may negatively impact body composition long-term. Finally, consuming the equivalent of roughly three to four drinks in a sitting may reduce the rate of muscle protein synthesis by up to 50 percent, and may also impede the anabolic response to high-protein meals as well.”
Bottom line: Drinking enough to catch a buzz will likely cause a negative impact on your fitness regimen, but a glass here and there shouldn’t hurt.