Case Study

A 45-year-old woman came to see me in the clinic for difficulty losing weight.  She has been on a low carb, ketogenic diet for 6 months but has lost very little weight and feels tired and sluggish.  She thinks she has a prolonged case of the “keto flu.”

She consumes between 30-50 grams of carbohydrate daily, but on further questioning I discovered that her primary vice was alcohol.  She was thrilled to discover that alcohol is “low carb” and started making what she calls “keto cocktails” this past summer and has continued to have 1-2 of these drinks almost daily.

I reviewed her labs and found that her liver function results were mildly elevated, her triglycerides had jumped up 20 points, and her body weight has been the same over the past year.

Why Alcohol is “Anti-Keto” and Inhibits Fat-burning

Ok people, it’s time for me to throw the hammer down. Counting carbs and net carbs is a good general rule of thumb which I recommend in my book and in my clinic, but there are some foods and substances that exert their physiological effects independent of their carbohydrate content, and alcohol is one of these. If you want to be in ketosis and allow your body to burn your own body fat for energy, you need your liver to be able to convert fatty acids released from your fat cells into ketones. When you drink a “keto cocktail” that is listed as having just a few carbohydrates, the alcohol goes straight to the liver to be metabolized and this actually impairs ketone production.

I would actually argue that alcohol, regardless of its carb content, is one of the most anti-keto, anti-fat burning substances you can consume. If you want a substance that enhances ketosis, you are better off using caffeine.

This woman’s ketogenic diet was a failure because of her regular “keto cocktail” consumption. Her liver became mildly inflamed and could not convert fats into energizing ketones. This happens even if your liver tests are normal. Women in particular whose livers are too busy breaking down alcohol, usually can’t remove other toxins either. The inability to remove toxins often leads to the accumulation of more body fat. She also reports her sleep being compromised. We can thank alcohol for that also since it reduces deep phase sleep and destroys REM (rapid eye movement) sleep.

In other words, alcohol significantly reduces the intrinsic properties of sleep that actually can promote fat burning in addition to multiple other benefits like improved glucose metabolism, enhanced mood, and cognitive function.

Now having said all this, if you are having the occasional cocktail, making a “skinny” or keto margarita like this recipe is far better than a regular one since most drink mixes have high fructose corn syrup which is an additional toxin to the liver.  By the way, if you order a “skinny margarita” at a bar or look at most online recipes, they use agave nectar as the sweetener.

Agave nectar may sound natural and healthy but it has more fructose than virtually any other sweetener including high fructose corn syrup.

There is nothing “skinny” about a skinny margarita made with agave syrup.  I have used raw honey or maple syrup to sweeten my margaritas.  Even plain sugar would be preferable to fructose or agave syrup.

Now you might tell me that “yeah, but I know someone who drinks daily and is losing weight on keto.” I believe you. There is individual variability depending on your liver’s ability to filter toxins, your cell’s mitochondrial function, your level of insulin sensitivity, etc. In other words, some people’s bodies are primed for fat-burning and a low to even moderate amount of alcohol consumption won’t get in the way. I would still argue that these individuals would be even leaner, fitter, and healthier if they quit or cut back alcohol further.  That’s why my patients who are elite athletes avoid alcohol altogether or consume in extreme moderation (few drinks a year).

I’ve noticed that alcohol absolutely wrecks my aerobic performance when I exercise. My power output on a bike, my running times, my heart rate, and any other objective or subjective metric I follow hits the tank and the same thing is noted by several of my patients and colleagues who measure metrics as closely as I do, like my good friend Dr.Peter Attia.  So just like I mentioned alcohol dampens the therapeutic and restorative impact of sleep, it also impairs exercise performance and its health benefits.

Since I measure my ketones regularly, I have seen that alcohol significantly inhibits my ability to produce ketones and burn body fat. I typically can get into ketosis with a 12-14 hour fast when I’m staying physically active and eating the way I should. If I add in keto-friendly, low carb alcohol, it can take me up to a few days before I’m back to burning fat again.  I’ve had patients report the same thing.

What About Alcohol’s Health Benefits?

In regards to alcohol’s impact on reducing heart disease risk and possibly enhancing longevity, this is the subject of a future post.  It is not an easy topic and most studies that do support benefit contain multiple confounders.  For example, some studies that show regular red wine consumption lowers heart disease risk upon further analysis show that red wine consumers also tend to be more health conscious (exercise more often and eat healthier) and belong to a higher socioeconomic demographic with better access to health care.  It’s not clear that the red wine alone is what lowers heart disease risk in light of these associated factors that also improve health and increase lifespan.

In this particular case study, I’m speaking more specifically about alcohol’s impact on the body’s ability to burn body fat.

The majority of my patients and people I know who drink regularly tend to carry extra body fat not only because of the multiple metabolic reasons we discussed already, but because regular alcohol consumption also lowers our willpower and inhibitions, leading us to eat the wrong foods at the wrong times, typically later at night.

Maybe some of these patients may go on to live long and healthy lives due to some of the heart healthy benefits of alcohol, but they’ll tend to do it with extra inches around their waist.

Back to Case Study

This patient was not keen on quitting her evening cocktail.  She said she enjoys her drinks, but she is also frustrated with her weight and concerned about her liver.  With some convincing, we agreed upon a 6 week trial of her quitting alcohol completely and re-measuring her labs and weight.  The results were compelling.  Her liver tests completely normalized, she lost 8 pounds, and she reported improved sleep, energy and mood.  In addition, she completely lost any urge to have a drink.

As a physician, I don’t like to push patients to completely eliminate foods and substances (like alcohol) they truly enjoy unless there is evidence of significant harm.  Sometimes implementing a limited trial with before and after labs and a subjective assessment (sleep, energy, etc.) is more convincing than anything I can tell them.

I never had plans to make this patient completely eliminate alcohol from her life, but thought we could eventually cut down her overall weekly amount.  However, once she realized that these previously “comforting” cocktails were the root cause for why she lacked energy and struggled to lose weight, she was able to completely let go of this habit.


If you want to get technical, then alcohol is a substance that can be low in carbohydrate content, particularly spirits like whisky, tequila, and vodka, versus beer which is higher in carbohydrates.  But why do we care about alcohol or any food being “low carb?”  It’s because we want to suppress the excessive release of the fat-storing hormone, insulin.  What we really care about is the ability of a specific food or substance to help us burn rather than store fat.  So it might be more accurate to define alcohol as a low carb, high body fat-storing substance.

High fructose corn syrup (HFCS) is another example where terminology can be misleading.  HFCS is low on the glycemic index because it does not cause a rapid rise in glucose.  This is because it goes straight to the liver and does its damage there.  I’m a big fan of tracking nutrition using Apps and online calculators, but don’t kid yourself into using these tools to justify the intake of  toxic foods that are disguised as low carb, low glycemic, keto-friendly, etc.

In summary, alcohol inhibits ketosis and fat burning by some of the following mechanisms:

  • Interferes with ketosis given its direct effect on the liver which is where ketosis occurs
  • Inhibits the liver’s ability to remove toxins which can trigger increased body fat storage.
  • Impairs the fat-burning and overall health-promoting effects of sleep
  • Reduces exercise performance, which means reduced fat-burning during exercise sessions.

Again, there is significant individual variation in alcohol’s impact on metabolism and overall health.  I would encourage all regular drinkers to consider a limited trial to see if removing or significantly reducing alcohol intake has beneficial effects, such as loss of body weight, improvement in blood pressure, lipids and glucose, and overall increases in energy.