The ketogenic diet, characterized by its low-carbohydrate, high-fat composition, has gained considerable popularity as a weight-loss and metabolic management strategy. This dietary approach drastically limits carbohydrate intake, compelling the body to enter a metabolic state called ketosis, where fat becomes the primary energy source. Given the stringent carb restrictions, many individuals embarking on a keto journey find themselves perplexed about the role of sugar. This article delves into the intricacies of sugar consumption on a ketogenic diet, exploring various sugar types, their impact on ketosis, and practical strategies for making informed choices.
Understanding the Ketogenic Diet
The ketogenic diet is an incredibly low-carb, moderate-protein, and high-fat diet. It typically contains 70% fat, 20% protein, and only 10% carbs. The daily carb limit varies depending on the specific type of keto diet being followed. Several variations exist, including:
- Standard Ketogenic Diet (SKD): This is the most common version, characterized by very low carb intake, moderate protein, and high fat.
- Cyclical Ketogenic Diet (CKD): This diet is similar to the SKD but allows for slightly more carbs through periods of high-carb refeeds, usually one or two days a week, to help replenish glycogen stores in the body. For the rest of the time, you follow a standard keto diet plan.
- Targeted Ketogenic Diet (TKD): This diet allows for small amounts of carbs before and after workouts.
- High-Protein Ketogenic Diet: Similar to the standard ketogenic diet, but includes more protein. The ratio is often around 60% fat, 35% protein, and only 5% carbs. It’s suitable for people who want to emphasize their protein intake while remaining in ketosis.
Another variation is a specialized version of the diet that is primarily used by athletes and bodybuilders. This diet highlights the importance of getting the right kinds of fats, proteins, and carbs, rather than simply focusing on amounts.
When a person drastically reduces their carbohydrate intake and replaces it with fat, the body enters a metabolic state called ketosis, where ketone bodies are produced from fat stores. These serve as a replacement for the energy usually produced by the breakdown of carbohydrates.
As well as the keto diet aiding weight loss, it is also associated with other health benefits. Research comparing the keto diet with a low-fat diet has shown that people on the keto diet not only lose weight in the long-term but their triacylglycerol levels and blood pressure fall.
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In the state of ketosis, glucose levels fall to a level that is too low for fat oxidation to occur and for glucose to be supplied to the central nervous system.
Sugar and Ketosis: A Delicate Balance
Nutritional ketosis, the state where your body is primarily burning fat for energy instead of carbs, typically requires the consumption of less than 50 grams of carbs per day. The way ketosis works makes it difficult to provide an accurate estimate of the volume of sugar that will kick you out of ketosis. Generally, the more sugar you consume, the more difficult it will be for your body to remain in ketosis. However, some people may be able to consume slightly more sugar and still remain in ketosis. This is because factors such as physical activity, genetics, and metabolic health can affect how efficiently your body uses carbs. Any sugar that puts you over your daily carb limit is not ideal on the keto diet.
Natural vs. Added Sugars
It's essential to distinguish between naturally occurring sugars and added sugars. Naturally occurring sugars are found naturally in foods such as fruits (fructose), starchy vegetables (glucose), and dairy products (lactose). Keto fruits, such as berries, are a good example of how sugar can be consumed in moderation on the keto diet. Added sugars are any sweeteners that are not naturally present in a food or beverage and are added during processing or preparation. They are found in a variety of products such as soft drinks, candy, pastries, and sauces. When you are on a strict keto diet, it’s advisable to limit or completely avoid added sugars while also keeping a close eye on your overall sugar intake (including naturally occurring sugars). Some forms of sugar may be allowed on the keto diet, but it’s important to always keep track of your daily carb limit and choose your sources wisely.
The Impact of Sugar Elimination
How the body reacts to the elimination of sugar depends on how much a person ate previously and whether they eat complex carbohydrates, which are broken down into simple sugars to provide energy. Initially, a person who eats sugary foods such as muffins and donuts may crave such foods because sugar is no longer available to stimulate the brain, explains Quebbemann. At first, the elimination of glycemic-rich foods would cause tiredness and lethargy, but that would only last a few days. The absence of sugar would trigger the liver to start producing ketones within three to five days, which is when the body starts to enter ketosis and burn fat. Some people even experience “keto flu,” which refers to the headaches, cramps, and fatigue that can develop and last for around a week.
Acceptable keto-friendly sweeteners.
For those who are asking “can I really not add sugar to my tea during keto?” there are artificial sweeteners that have little to no impact on blood sugar, and they can be used in moderation while still maintaining ketosis.
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- Stevia: The stevia plant is native to South America but is grown worldwide. You will see stevia on grocery shelves under brand names like Truvia and PureVia. Stevia works well in coffee and tea. It is about 200-400 times sweeter than table sugar. Possible risks include bloating, dizziness, nausea, and numbness. Stevia may also lower blood sugar or blood pressure. Stevia, monk fruit, and erythritol are some of the best low-carb sweeteners for the keto diet.
- Monk Fruit: Monk fruit (Luo Han Guo) comes from a plant native to China and is sold under brand names like Monk Fruit in the Raw and PureLo. This sweetener is 100-250 times sweeter than table sugar, contains no calories, and has 0.5 grams of carbohydrates per teaspoon.
- Erythritol: Erythritol is a naturally occurring sugar alcohol found in fruits and fermented foods. It has 0 calories and is about 60-80% as sweet as table sugar. Erythritol does not raise blood sugar or cause tooth decay. It may lower sugar consumption, but more research is needed. You can use erythritol as a substitute for table sugar in beverages and several recipes.
- Xylitol: Xylitol is a sugar alcohol that is as sweet as table sugar but has fewer calories and carbohydrates. Xylitol might cause cramps and diarrhea if you consume too much.
- Maltitol: Maltitol is a sugar alcohol that is about 75-90% as sweet as table sugar but has fewer calories. Maltitol can be helpful for weight loss because it is low in calories. It might also improve dental health, but the data is mixed.
- Yacon Syrup: Yacon syrup is made from the roots of the yacon plant, commonly grown in South America. Yacon syrup is a source of fructooligosaccharides (FOS), a type of soluble fiber your body does not digest. Soluble fiber lowers cholesterol, which may protect against heart disease. Yacon syrup works well in coffee, tea, and salad dressing.
Foods and drinks
Just because foods or drinks contain low-carb sweeteners does not mean they are keto-friendly. Not all foods and drinks that use these sweeteners are keto-friendly. Therefore, while navigating the keto diet, it may be confusing to know how to deal with sugar.
As with most diets, certain foods must be avoided on the keto diet if a person is going to reap benefits. Carbohydrate-rich foods such as pasta, rice, and potatoes must all be avoided, as well as foods with a high sugar content such as fruit, soda, beer and chocolate. Unprocessed meats may be eaten, along with seafood, fish and eggs.
The Science Behind Ketogenic Diets and Sugar Restriction
Recent research has shed light on the metabolic effects of ketogenic diets and sugar restriction. A study published in Cell Reports Medicine (Hengist, A., Davies, R. G., Walhin, J., et al., 2024) investigated the impact of ketogenic and low-free-sugar diets on glucose tolerance, lipid metabolism, peripheral tissue phenotype, and the gut microbiome.
The researchers randomized 60 healthy adults to a ketogenic or low-free-sugar diet for 12 weeks. The ketogenic and low-free sugar groups reported consuming less than 8% and 5% of their total energy as carbohydrates, respectively. At 12 weeks, study participants in both intervention groups lost fat mass due to lowered energy intake. The low-free sugar group had reduced total energy intake, total cholesterol, and low-density cholesterol (LDL-C) levels compared to controls. Fasting glucose levels were also reduced in the ketogenic group at four weeks until ultimately returning to baseline levels at 12 weeks.
The study findings emphasize that low carbohydrate or free sugar intake preserves physical activity energy expenditure (PAEE) in healthy adults. Reducing free sugar intake by 1% caused self-reported energy intake to decrease by 14 kcal/day, corroborating previous research. Reduced energy intake led to decreased fat and total body mass, thus indicating that these dietary interventions are effective long-term strategies for weight loss. However, the ketogenic diet only observed gut microbiome shifts and unfavorable metabolic changes at peripheral and whole-body levels.
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In the ketogenic group, lower concentrations of amino acids (AAs) were used to synthesize glucose and higher levels of branched-chain AAs were observed. The ketogenic group also exhibited higher levels of the inflammatory marker C-reactive protein (CRP) at week four. These changes were not observed by week 12 despite these individuals continuing to exhibit ketosis throughout the study period.
Benefits of Cutting Out Sugar
Eliminating sugar from the diet can be challenging since it is found in foods people would not necessarily think of as containing sugar such as tomato sauce and even veggie burgers. However, if a person does cut sugar out of their diet, the health benefits will be almost immediate.
Quebbeman says that although it is common for people on the keto diet to start losing weight, doctors are still divided over whether this is healthy in the long-term. In fact, eliminating sugar, but including complex carbs helps to maintain a healthy insulin level.
Potential Downsides and Considerations
Some people even experience “keto flu,” which refers to the headaches, cramps, and fatigue that can develop and last for around a week. There is also some controversy regarding the inclusion of artificial sweeteners in the keto diet.