Matthew Barnes, Ph.D., studies the effects of alcohol and exercise at New Zealand's Massey University. While there isn't a ton of research on how alcohol affects endurance training long-term, Barnes’ research has shown there’s evidence that drinking alcohol directly after exercise is likely to inhibit recovery and impair performance, especially for endurance athletes. After all, alcohol is a toxic substance, Barnes says. “It impacts the immune system, hormonal system, musculoskeletal system, and nervous system.” Here are a few more ways it negatively affects the body:
1. It messes with your blood sugar levels.
A night of drinking can lead to hypoglycemia, or low blood sugar levels, in the morning, says Greg Whyte, professor in applied sport and exercise science at Liverpool John Moores University. This is also the reason drinkers tend to crave sugary, high-carb foods when hungover. This alternating in glucose handling can lead to a drop in energy levels, which isn’t good before a long training run.
2. It can affect your heart.
If you exercise intensely after drinking alcohol, it’s possible to induce unusual rhythms in the heart, which is not only detrimental to performance but your health in general, Whyte says.
3. It can lead to poor sleep patterns.
Sleep, which as you’ve probably heard is a pretty crucial factor of overall health and athletic performance, is also altered by alcohol. Drinking can disrupt sleep patterns, decreasing the quality and total hours slept, Barnes says. And research shows that sleep deprivation for athletes in particular can lead to poor performance in training and competition. So even if you abstain from drinking the night before a race, drinking the night before a long run (or at any point during your training) could harm your race day performance.
4. It can pack on the pounds.
If you continue to drink through your training plan, the additional boozy calories (providing no nutritional value) can cause you to gain weight and adversely affect your overall performance, Whyte says. Some experts say that for every pound you lose, you shave two seconds off your mile time.
5. It can cause additional stress on your body.
And let’s not forget about our brains. “A big race, like a marathon, stresses the brain, and alcohol is a physiological stressor,” says Leigh Leasure, Ph. D., an associate professor of psychology at the University of Houston. “So if you don’t drink, that’s one less stressor for your brain to deal with.”
6. It can cause nasty hangovers.
As a final important point... the more you drink, the worse the hangover. Alcohol dehydrates you, which can lead to headaches, stomach cramps, and overall fatigue — all symptoms that you want to avoid before any long training run, and especially on race day.