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Gastric Bypass and Alcohol: Drinking After Surgery

Gastric Bypass and Alcohol: Drinking After Surgery

As the prevalence of obesity increases, so does the number of those seeking bariatric surgery in hopes of losing weight and lowering risk for disease. Gastric bypass surgery, although effective, is no walk in the park.

This surgery, like all surgical procedures, comes with risks and potential side effects. Alcohol in particular may be problematic after bariatric surgery. If you had or are considering gastric bypass surgery, here are some things to consider before consuming alcohol.

Gastric Bypass and Alcohol Absorption

The anatomy of the digestive tract is significantly altered after gastric bypass. Therefore, the body absorbs alcohol differently and is more sensitive to its effects following surgery.

Before gastric bypass surgery, alcohol digestion begins in the stomach. There, an enzyme called alcohol dehydrogenase (ADH) begins breaking down alcohol as it sits in the stomach. Food in the stomach holds alcohol there longer, allowing it to break down further before it enters the small intestine, where 80% of alcohol is absorbed into the bloodstream.

After gastric bypass surgery, around 95% of the stomach is bypassed, leaving an egg-size pouch that serves as a new stomach. Therefore, alcohol passes almost immediately from the stomach to the small intestine, where it then moves into the bloodstream. Post-op patients are also instructed not to eat food and drink fluids at the same time, which means it’s likely that no food will keep alcohol in the stomach.

Spending little to no time in the stomach means very little alcohol is broken down by ADH in the stomach, and more alcohol makes it into the bloodstream in a short amount of time.

It will take less alcohol to make you intoxicated after bariatric surgery.

After gastric bypass, alcohol enters the bloodstream rapidly

One danger of gastric bypass and alcohol consumption is that a higher concentration of alcohol ends up in the bloodstream much more quickly than it probably did prior to surgery. In fact, a recent study found that participants who recently had gastric bypass reached a blood alcohol content (BAC) greater than 0.8 within only 10 minutes of consuming one small dose of alcohol.

At this level of intoxication, symptoms include:

  • Loss of coordination
  • Slurred speech
  • Memory loss
  • Nausea and vomiting
  • Blackouts
  • Passing out

Another study examined the effects of alcohol on a group of eight women who had roux-en-y gastric bypass (RYGB) five or fewer years prior to the study, as well as nine women scheduled to have RYGB in the near future. Following the study, researchers concluded that drinking two alcoholic beverages following gastric bypass carried the same effects as drinking four alcoholic beverages prior to surgery.

It may be more difficult to reach sobriety after gastric bypass.

It takes longer for alcohol to leave your system after gastric bypass

Although alcohol enters the system rapidly following gastric bypass, it actually stays in your system longer.

Research shows that following gastric bypass surgery, it takes longer for the body to clear alcohol from its system. In other words, you’re likely to feel symptoms of intoxication for a longer period of time and it may be more difficult to sober up.

Because it takes longer to reach sobriety, many experts recommend that all gastric bypass patients avoid driving after consuming alcohol altogether.

Gastric bypass increases the risk for alcohol-related blackouts

Your body is dramatically sensitive to alcohol after gastric bypass. This means you can easily reach extreme symptoms of intoxication with only a small amount of alcohol. One extreme symptom that is reported more often after surgery is blackout.

Blackout generally refers to memory loss while a person is intoxicated. This occurrence is usually the result of rapidly increasing BAC. Blackouts are not a pleasant experience.

To avoid blackouts, limit yourself to one alcoholic beverage.

You may experience low blood sugar when drinking alcohol.

Alcohol and Low Blood Sugar

For the first several months after surgery, it’s easy to experience low blood sugar. Symptoms of low blood sugar include:

  • Loss of coordination
  • Poor vision
  • Slurred speech
  • Confusion
  • Unconsciousness

Drinking alcohol increases the risk for low blood sugar after gastric bypass, because it can deplete glycogen in the body. Furthermore, people with recent gastric bypass surgery consume little to no food when they drink alcohol.

To prevent low blood sugar after gastric bypass, avoid alcohol for the first several months post-surgery.

Alcohol and Excess Calories

It’s important to remember that alcohol is calorically dense. Just one 5-ounce glass of wine contains over 100 calories. Mixed drinks that contain soda, juice, or sugary drink mixes pack even more calories. Excess calories from alcohol can slow weight loss dramatically after gastric bypass.

Gastric bypass may increase risk for alcohol abuse disorder.

Gastric Bypass and Alcohol Addiction

Increased risk for alcohol use disorder (AUD) and addiction is a concern after gastric bypass. Some studies have shown patients to be most at risk after two or more years following surgery. Theories about why risk for AUD is higher after gastric bypass include:

  • Changes to alcohol metabolism that make it more addictive
  • Addiction transfer

The body metabolizes alcohol differently after gastric bypass surgery, which may increase risk for addiction. First, the body’s heightened sensitivity to alcohol may cause higher consumption levels that eventually lead to addiction.

Some researchers believe that neurological changes following surgery increase risk for alcohol abuse. This theory suggests that the rewarding effects of food are replaced by the effects of alcohol. However, more research is needed.

Addiction transfer is the notion that patients were possibly addicted to food before gastric bypass surgery, and that addiction is passed on to alcohol or other vices following surgery. However, many studies have debunked this theory, mainly because AUD and addiction most often occur at least two years following bariatric surgery.

Be mindful symptoms of alcohol abuse, and talk to your doctor if you experience:

  • Memory impairment
  • Dependence or fixation on alcohol
  • Risky behavior (drunk driving, for example)
  • Inability to stop drinking
Take care when drinking alcohol after gastric bypass.

Key points to stay safe with alcohol after gastric bypass

  • Alcohol enters the bloodstream quickly and dramatically after gastric bypass surgery
  • Your tolerance is likely much lower
  • It takes longer for alcohol to leave your system
  • Alcohol increases risk for low blood sugar
  • Alcohol is high in excess calories
  • Talk to your doctor if you notice symptoms of alcohol abuse

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Breanna Woods, MS, RDN


Breanna Woods is a registered dietitian with over 5 years of experience in the clinical field. She has a master’s degree in food and nutrition, and strives to guide others to a healthy lifestyle.

Gintas Antanavicius, MD, FACS, FASMBS

Medical Reviewer

Dr. G is a co-founder of BariBuilder. A US-based expert surgeon with over 10 years of bariatric experience, he regularly publishes research in medical journals like SOARD, Obesity Surgery, etc.