The apparent consumption of alcohol by Australians equates to 2.72 standard drinks per person, per day. And there’s a fair chance that as we come into the silly season with Christmas parties, New Year’s Eve, and summer BBQs, that consumption is slightly above average over this time of year. Alcohol is the 6th highest contributor to burden of disease in Australia, responsible for 4.5% of the burden of disease & injury. Beyond the effects on overall health with excessive consumption, alcohol and physical fitness and performance really don’t go hand in hand. Now is an appropriate time to talk about alcohol and the impact it could be having on your training and health & fitness goals.

Effect on strength training

Alcohol ingestion around strength and resistance training has negative effects on muscle building and recovery, and other aspects of the endocrine response, ultimately diminishing strength gains. This interference in muscle growth is especially evident in type II muscle fibres – the explosive, force-generating fibres used for sprinting, jumping, and lifting weights. Alcohol ingested after resistance exercise reduces anabolic signalling, hampering desired muscular adaptations¹. When you disrupt the ideal anabolic environment – suppressed growth hormone secretion & reduced testosterone bioavailability – efficient healing of the muscles cannot occur following resistance training². As a result, you will feel sore longer and your muscles will take longer to heal, compromising your adaptations to that training bout. In 2017, 10 males & 9 females performed heavy resistance exercises before ingesting alcohol or a placebo. The exercise bout elicited MTORC1 signalling, but in men the exercise-induced anabolic signalling was reduced following alcohol consumption¹. Instead of increasing testosterone levels which usually accompanies resistance exercise to help grow the muscles, alcohol increases the hormone cortisol (the same hormone that causes stress). Long-term alcohol use can also prevent increases in muscle androgen receptor content from resistance training² which decreases the body’s ability to use testosterone, regardless of how much is circulating.

In a 2014 study³, following a training session comprising strength exercises, continuous cycling, and high intensity intervals, subjects were given a heavy dose of alcohol (1.5g/kg equivalent to 12 standard drinks over a 3 hour period) accompanied by either protein or carbohydrates. Post-workout protein synthesis was decreased by 24% and 37% in these respective groups (see the table below), and peak power was still below baseline 36hrs later. Consuming even moderate amounts of alcohol after muscle-damaging exercise magnifies the loss of force. Alcohol consumption of 1g/kg following eccentric exercise led to double the loss in dynamic & static strength outputs even after a 60hr recovery period when compared to the use of a placebo⁴. If you repeatedly disrupt the muscle building and recovery processes, your overall training outcomes are going to be significantly disrupted.

Effect on aerobic training

Alcohol consumption impairs the metabolic process during exercise, decreasing the use of glucose & amino acids by skeletal muscles, which adversely affects energy supply, and consequently exercise performance⁵. High doses of alcohol impair the liver’s ability to produce glucose (hepatic gluconeogenesis). Alcohol is processed by the liver, so when it is busy breaking down alcohol, it is less efficient at producing glucose; lactate & glycerol uptake is decreased; and muscle glycogen uptake and storage is reduced⁶. Glucose availability plays a pivotal role in endurance performance, and readily available energy stores are necessary to fuel exercise and recovery, so alcohol really impacts your ability to fuel your workout.

Alcohol acts as a peripheral vasodilator, expanding the blood vessels. This increases fluid loss, exacerbating dehydration (which is probably already present since alcohol is a diuretic), and interfering with the body’s ability to thermoregulate⁶. Thus, alcohol has been repeatedly shown to decrease work tolerance in warm and in temperate conditions. One of the other ways alcohol can affect your athletic performance, is through the detrimental effects of a hangover on exercise. A hangover can reduce aerobic performance by 11.4%.

Overall, alcohol is thought to impair muscle work capacity and result in decreased performance levels (slower running and cycling times), impair thermoregulation during exercise, and increase onset of fatigue during high intensity exercise.

Effect on Weight loss goals

You’ve probably heard alcohol often referred to as “empty calories”, this is because every 1g of alcohol provides 7 calories (on the other hand, protein and carbs provide 4cal per gram, while fat comes in at 9cal/g). But the caveat is that alcohol has no other nutritional value. Because of its relatively high energy density, for some people the contribution of alcohol to their total energy intake is significant. Additionally, alcohol is often consumed with foods; either as part of a meal or accompanied by snacks & foods, which further increases the associated energy intake. Consuming large amounts of alcohol while trying to maintain a calorie deficit when wanting to lose weight would be extremely challenging, the below table shows the kilojoule count of popular alcoholic drinks. If the consumption of other foods or drinks is reduced to bank up the extra calories for alcohol intake, this could lead to deficiencies in other key nutrients⁷.

In addition to being a readily accessible source of energy, alcohol has a number of effects that bear ramifications for metabolism⁶. Alcohol influences carbohydrate and fat metabolism by displacing them as energy sources⁸ and inhibiting fat burning⁷. The body prioritises breaking ethanol down to flush it out of the body, and while this is occurring the metabolism of other macronutrients, especially fat, is slowed. When exercising at low intensity, most of the energy would typically come from fat oxidation, but after drinking alcohol the liver cannot convert the fat to energy and so it is stored instead. This suppressed fat burning is regarded as a risk factor for weight gain & abdominal obesity⁸. Concerningly, alcohol particularly decreases fat burning around the abdomen, and more central adiposity is associated with multiple health risks.

Fear not, you don’t have to abstain from alcohol completely. It can be consumed in moderation (up to 3-4 std. drinks) without affecting results, as long as you factor in the calories to your total daily energy intake.

Takeaway

Just because you drink alcohol doesn’t mean you have to skip a workout, in fact you’ll want to keep up the physical activity at this time of year to maintain health, weight and fitness. But you do want to make sure you’re recovered before stressing the body further. Moderate drinking isn't likely to affect how you fair in the gym or on the field the next day, but once you move beyond moderate consumption to three or four drinks your performance might be affected in a few different ways. It’s best to avoid drinking if you’re looking to be at your physical peak the next day. Avoid drinking following heavy training sessions, and ensure your protein intake is adequate to limit the reduction in protein synthesis.

Remember to always drink in moderation and factor the calories into your total caloric. Generally, if you’re drinking enough to get drunk then you are drinking enough to have a negative impact on your performance output and body composition.

References