How exactly does alcohol cause weight gain?

For many, a glass of wine after a long day or a couple of pints at the pub feels like a harmless indulgence. But when you’re trying to lose weight, those casual drinks might be sabotaging your efforts in more ways than you realise. From empty calories to hormone disruption, alcohol poses unique challenges to weight loss, some of which are hidden beneath its liquid allure.

The calorie conundrum

One of the most obvious issues with alcohol is its calorie content. Alcoholic drinks are often described as “empty calories” because they provide energy without any nutritional value.¹ For example, beer, wine, and cocktails  mixed with fizzy pop and juices can provide you with calories that may be seen as excessive.²

For comparison, a healthy snack, regardless of what it may be, could contain the same amount or less calories than a pint of beer. But while a snack provides nutrients that fuel your body, alcohol offers no such benefit. Instead, those extra calories are stored as fat, often in the abdominal area, giving rise to the dreaded “beer belly”, especially in men.³

How alcohol hijacks metabolism

The impact of alcohol goes beyond calorie count. Once consumed, alcohol becomes your body’s preferred energy source. This means that instead of burning calories from carbohydrates or fats, your body focuses on metabolising the alcohol first.⁴

As a result, excess glucose and lipids are stored as fat. Over time, this metabolic shift can make it harder to lose weight, as your body prioritises processing alcohol over burning stored fat.

Your liver, which is the multitasking organ responsible for metabolising fats, carbohydrates, and proteins while filtering out toxins like alcohol, also takes a hit, consequently affecting metabolism. Excessive drinking can overwhelm your liver, leading to a condition called alcoholic fatty liver.⁵ This impairs the liver’s ability to store and metabolise energy effectively, making weight loss an even steeper uphill battle.

Alcohol’s effect on appetite and food choices

Ever noticed how you crave greasy, calorie-laden foods after a few drinks? Alcohol affects your brain’s hunger signals, often triggering overeating. A study found that mice given ethanol—a form of alcohol—showed a significant increase in food consumption.⁶

This isn’t just about biology; alcohol also lowers inhibitions, leading to poor decision-making.⁷ The slice of pizza or bag of chips that might seem indulgent on a sober day becomes irresistible after a few rounds at the bar.

Hormonal interference

Alcohol doesn’t just mess with your metabolism and appetite. It also disrupts your hormones, particularly testosterone.⁸ Studies have shown that low testosterone levels are linked to higher body fat and an increased risk of metabolic syndrome—a condition characterised by high blood sugar, cholesterol, and blood pressure, as well as obesity.⁹

Sleep disruption and weight gain

Although a nightcap might feel like the perfect way to unwind, alcohol can actually impair your sleep. While it may help you fall asleep initially, it disrupts your sleep cycle, leading to more periods of wakefulness throughout the night.¹⁰

Poor sleep impacts hormones like ghrelin and leptin, which regulate hunger and satiety. When you’re sleep-deprived, your body produces more ghrelin (the hunger hormone) and less leptin (the satiety hormone), driving you to eat more than you need.

The impulsivity connection

Interestingly, research suggests that alcohol consumption has a stronger impact on weight loss in individuals with high impulsivity. A study found that impulsive individuals who reduced their alcohol intake experienced greater weight loss compared to their less impulsive peers.¹¹ This is likely because alcohol exacerbates impulsive behaviour, leading to unplanned overeating or indulging in high-calorie foods.

How to manage alcohol and weight loss

Reducing alcohol doesn’t mean you have to abstain completely. Small changes can make a big difference:

• Choose lower-calorie options: Opt for spirits with soda water or light beers instead of sugary cocktails.

• Pace yourself: Alternate alcoholic drinks with water to stay hydrated and reduce overall intake.

• Limit drinking to special occasions: Reserve alcohol for celebrations rather than making it a daily habit.

• Be mindful of your triggers: If drinking leads to overeating, plan meals ahead or keep healthier snacks on hand.

The numan take

While alcohol doesn’t have to be off-limits, understanding how it affects your weight loss journey is key to making informed choices. From empty calories to its impact on most aspects of health, alcohol can be a significant roadblock to reaching your goals. But with mindful consumption and a focus on balance, it’s possible to enjoy the occasional drink while staying on track. 

References

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2. Website NHS. Calories in alcohol [Internet]. nhs.uk. 2024 [cited 2025 Jan 3]. Available from: https://www.nhs.uk/live-well/alcohol-advice/calories-in-alcohol

3. Schröder H, Morales-Molina JA, Bermejo S, Barral D, Mándoli ES, Grau M, et al. Relationship of abdominal obesity with alcohol consumption at population scale. Eur J Nutr [Internet]. 2007;46(7):369–76. Available from: http://dx.doi.org/10.1007/s00394-007-0674-7

4. Jiang L, Gulanski BI, De Feyter HM, Weinzimer SA, Pittman B, Guidone E, et al. Increased brain uptake and oxidation of acetate in heavy drinkers. J Clin Invest [Internet]. 4 2013;123(4):1605–14. Available from: https://www.jci.org/articles/view/65153

5. Osna NA, Donohue TM Jr, Kharbanda KK. Alcoholic Liver Disease: Pathogenesis and Current Management. Alcohol Res. 2017;38(2):147-161. PMID: 28988570; PMCID: PMC5513682.

6. Lopez MF, Grahame NJ, Becker HC. Development of ethanol withdrawal-related sensitization and relapse drinking in mice selected for high- or low-ethanol preference: Withdrawal sensitization and relapse drinking in hap and lap mice. Alcohol Clin Exp Res [Internet]. 2011;35(5):953–62. Available from: http://dx.doi.org/10.1111/j.1530-0277.2010.01426.x

7. Brevers D, Bechara A, Cleeremans A, Kornreich C, Verbanck P, Noël X. Impaired decision-making under risk in individuals with alcohol dependence. Alcohol Clin Exp Res [Internet]. 2014;38(7):1924–31. Available from: http://dx.doi.org/10.1111/acer.12447

8. Rachdaoui N, Sarkar DK. Effects of alcohol on the endocrine system. Endocrinol Metab Clin North Am [Internet]. 2013;42(3):593–615. Available from: http://dx.doi.org/10.1016/j.ecl.2013.05.008

9. Wang C, Jackson G, Jones TH, Matsumoto AM, Nehra A, Perelman MA, et al. Low testosterone associated with obesity and the metabolic syndrome contributes to sexual dysfunction and cardiovascular disease risk in men with type 2 diabetes. Diabetes Care [Internet]. 2011;34(7):1669–75. Available from: http://dx.doi.org/10.2337/dc10-2339

10. Stein MD, Friedmann PD. Disturbed sleep and its relationship to alcohol use. Subst Abus [Internet]. 2006;26(1):1–13. Available from: http://dx.doi.org/10.1300/j465v26n01_01

11. Kase CA, Piers AD, Schaumberg K, Forman EM, Butryn ML. The relationship of alcohol use to weight loss in the context of behavioral weight loss treatment. Appetite [Internet]. 2016;99:105–11. Available from: http://dx.doi.org/10.1016/j.appet.2016.01.014