The Effects of Caffeine on the Keto Diet

Most of us can’t imagine our lives without coffee (or, in my case, pre-workout!). One of the most consistent questions I get when meeting with clients is regarding if and how caffeine affects body composition. In the past year, with the prevalence of the Keto Diet, these questions often become Keto-specific.

To give you context, the Keto Diet is a nutritional regimen that is characterized by a very low amount of carbohydrate and high amount of fat intake to throttle your body into ketosis. Your body is predisposed to utilizing carbohydrate as its primary substrate for metabolism, because, well, it`s the easiest to metabolize.

When you eat a carbohydrate, it is broken down into its primary glucose form (or fructose or galactose, depending on the carbohydrate ingested). If your body needs energy, you uptakes this glucose and send it down a series of metabolic reactions which ultimately give you ATP (adenosine triphosphate or the ultimate energy currency for the body). Or, if you aren`t in need of energy, your body stores this carbohydrate as glycogen or fat (glycogen is the storage form of carbohydrate that exists in the muscles and the liver as a backup fuel source for intense or long endurance activities).  You break the fat down when you need energy and are not ingesting any carbohydrate.

What happens when you don`t eat carbohydrates for an extended period of time? You have to break down fats (and protein). The breakdown of fats is called fatty acid oxidation and leads to the production of ketone bodies. Ketone bodies are the energy currency of fats. If you`re interested in the science, ketone bodies get converted into acetyl-Coenzyme A, which then completes the same energy transport chain as glucose. When your body primarily uses ketone bodies for energy, we say that your body is in a state of ketosis.

Breaking down fats increases your body`s metabolism because it has to work harder to complete the process, and the diet is popular because it isn`t restrictive. You can eat the same amount of calories (in some cases more), you just have to adhere to strict macronutrient guidelines. The standard ketogenic diet regulates 5% or less of your daily caloric intake as carbohydrates, 75% fats, and 20% protein.

But, back to the main point here: how does caffeine affect the ketogenic diet and metabolism in general? Caffeine is a stimulant, and is therefore going to increase your heart rate and raise your body temperature. This in turn increases general metabolism. In a study published in the Clinical Journal of Nutrition showed a statistical increase in the metabolic rate and in fatty acid oxidation in participants who ingested a minimum of 4mg of caffeine per kilogram body weight (1). A separate study in the Canadian Journal of Physiological Pharmacology determined that caffeine consumption increases the production of ketone bodies (2).


The issue with caffeine consumption and the keto diet is that most people like to ingest caffeine with a sugar of some sort, whether it be the lactose in cream or sugar in an energy drink or coffee. These carbohydrates can add up quickly if you are sticking to the standard ketogenic diet of less than 5% of your total diet. Also, if you are not used to the keto diet, you might already feel a bit shaky due to the lack of carbohydrate and the shock that can have on your body. My recommendation is to avoid caffeine for the first two weeks of starting the diet, and gradually incorporating it by 1mg./kg body weight per week thereafter until you have reached your comfortable amount. Pairing caffeine with a fat or protein-filled meal will help slow the effects as well.




Rachel Webb