The ketogenic diet, or "keto," is a high-fat, moderate-protein, and very low-carbohydrate eating plan designed to shift the body into a metabolic state called ketosis. In ketosis, the body burns fat for energy instead of carbohydrates. This dietary approach has gained popularity for its potential benefits, including weight loss and improved management of certain health conditions. However, successfully following a keto diet requires careful attention to macronutrient ratios, especially carbohydrate intake.
Understanding the Keto Diet and Ketosis
The primary goal of the ketogenic diet is to induce and maintain ketosis. This metabolic state is achieved by drastically reducing carbohydrate intake, typically to 20-50 grams per day. When carbohydrate intake is restricted, the body's glucose stores deplete, prompting it to turn to fat for fuel. The liver breaks down fat into ketones, which are then used as an alternative energy source.
Originally used to treat epilepsy, the keto diet is now a popular weight loss plan, in part because its focus on fat consumption can leave you feeling fuller and more satisfied than other diets.
How Ketosis Works
When your body depletes the stores of glucose (provided by carbohydrates) that it typically burns for fuel, it starts burning ketones, a form of energy made from fat. It takes a few days to fully enter a ketogenic state, during which a majority of the energy your body uses comes from ketones instead of carbohydrates.
As your body enters ketosis, you may experience side effects collectively referred to as “keto flu.” These symptoms include fatigue, upset stomach, headache, and dizziness, and they’re most common when a person is first entering ketosis. They usually subside once the body has adjusted to burning ketones instead of carbohydrates.
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The most accurate way to know if you’re in a ketogenic state is to test your blood or urine using test strips, available at drug stores and online. Handheld breathalyzers can also be used to check ketone levels, but this newer technology isn’t necessarily accurate.
Some people say they feel differently when they’re in ketosis. “You can usually tell,” says Florida-based registered dietitian nutritionist Franziska Spritzler, author of The Low-Carb Dietitian’s Guide to Health and Beauty. “You’re not as hungry.”
Falling Out of Ketosis and Getting Back In
Many keto diet plans recommend getting only about 5 to 10 percent of your daily calories from carbohydrates, which translates to between 20 and 50 grams of carbohydrates a day for most people. Exceeding that daily limit by consuming foods or beverages that are high in sugars or starches sends your body out of ketosis, as it returns to burning carbohydrates, which are its preferred source of fuel.
However, falling out of ketosis doesn’t mean starting from scratch. Though it can take several days to enter ketosis during the initial stage of the keto diet, it doesn’t take as long to return to ketosis after a slip, says David Bridges, PhD, assistant professor of nutritional sciences at the University of Michigan School of Public Health.
"Yes, if you go to your mother’s house and she made these delicious cinnamon rolls and you just have to have one, it will probably stop the process of generating ketones and take you out of ketosis temporarily,” he says. “But if it’s just one meal, and you go right back to your [keto] diet, you should be able to get back into ketosis fairly quickly.”
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The Role of Sugar in a Keto Diet
Given the low-carb nature of the keto diet, sugar intake must be carefully monitored. Sugar, a soluble carbohydrate, can quickly elevate carb intake and disrupt ketosis. With a readily available supply of carbs, the body will prioritize glucose for fuel, halting ketone production and hindering weight loss efforts.
To achieve and maintain ketosis, keto dieters must restrict their carbohydrate intake. Because the allowance for carbs is very low in keto, seasoned dieters say you have to make mindful food choices. While the ketogenic diet is not overly demanding, it does require meticulous tracking of your macros to ensure you’re staying within your daily carb allowance.
How Eating Sugar May Make You Feel on the Keto Diet
Eating sugar while in ketosis may cause side effects too. “You may experience some gastrointestinal distress,” says Dr. Bridges. “If you’ve been in ketosis for a while, your body may no longer be equipped to digest high-carbohydrate foods in the same manner it used to be.”
You may also experience symptoms of keto flu as you get yourself back into ketosis. And if you stop following the low-carb diet for more than just a meal or two, you’re likely to gain back some of the water weight you lost initially, says Bridges.
Eating sugar while in ketosis may also trigger a setback psychologically for some people, according to Spritzler. “I recommend staying low carb as much as you can, because when you get used to eating a certain way, you can get to the point where you really don’t crave sugar,” she says. “But if you go ahead and have a cheat day or a cheat meal, it can stimulate those pleasure centers in the brain. It can be difficult to get back on track without wanting that sweet treat again.”
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Bridges and Spritzler agree that eating a starchy meal or sugary dessert certainly could throw your body out of ketosis, and it might make you feel pretty lousy for a short time as well. But as long as you’re not indulging in high-carbohydrate foods regularly, the occasional treat shouldn’t derail your long-term plans for losing excess weight or keeping it off with the keto diet.
How Much Sugar Can You Have on Keto?
In summary, to answer how much sugar can you have, followers of a keto diet will want to make sure that their sugar intake keeps them remaining below the 50-gram daily carb limit.
On the keto diet, you’ll generally need to keep your daily carbohydrate intake to 20-50 grams of sugar. It may take some trial and error to achieve ketosis. Many folks prefer to start with a strict limit of 20 grams of sugar per day and then see how many grams they can take while still keeping their body in ketosis.
Identifying Hidden Sugars
Tracking sugar intake can be challenging, as sugar content isn't always obvious. Some foods naturally contain sugar, while others have added sugars that may be disguised on nutrition labels. Hidden sugars can easily sneak into your diet through processed foods, snacks, sauces, and salad dressings.
The nutrition label is a goldmine of information that can help you identify whether or not a food item is keto-friendly. To spot hidden sugars, look for ingredients like fructose, sucrose, lactose, and dextrose - basically, anything ending with “-ose” might be a form of sugar.
When tracking your sugar intake, don’t just list whatever’s on the nutrition label. You should be tracking net carbs, which means a little bit of math is called for.
Reading Labels and Recognizing Sugar's Aliases
At the beginning of keto, nutrition labels are your biggest ally. Always check the labels on packaged foods for the carbohydrate and sugar content. Remember that sugar can come in other forms and names, including sucrose, fructose, corn syrup, and dextrose.
Sugar isn’t always easy to spot in ingredient lists. That’s because it has so many names and variations. It would take a bit of studying to properly familiarize yourself with sugar and all its forms.
Natural Sugars vs. Added Sugars
By now, you probably noticed that sugar can come in many different forms. But it’s not just those“-ose” ingredients you should be mindful of. Natural sugars are those that exist naturally in whole foods. You’ll find them in fruits and dairy. On the other hand, added sugars are introduced to food during preparation or processing. Nutritionists do recommend proactively choosing to consume natural sugars in whole foods instead of food with added sugars.
Natural Sugars: Fructose and Lactose
Fructose is a natural sugar that is commonly found in fruits and vegetables, alongside the other natural sugars of sucrose and glucose. Fructose has the same amount of calories per gram as most sugars, which is 4 calories per gram. For example, apples are high in fructose and contain on average 19 grams of fructose naturally, coming in at around 95 calories per large apple. In contrast, mangos contain 24 grams of sugar fructose and have 107 calories, but also offer lots of vitamin C (75% of your daily recommended intake).
Lactose is also a naturally occurring sugar but is found mostly in dairy products, notably milk. For example, a 1 cup serving of whole milk contains, on average, around 13 grams of lactose. Lactose does not contribute too much flavor to these milk-based dairy items, and consequently, it is recommended that followers of the keto diet try to avoid lactose.
The Downside of Low-Fat Products
Many low-fat products have what's called a "health halo" effect. We view them as healthy, but to keep up the delicious, crave-worthy taste, manufacturers might add more sugar. Full-fat versions of foods are often more likely to be keto-friendly (and taste better, too).
Minimizing Processed Foods
The more whole a food is, the less likely it will contain hidden sugar (see salad dressings and pasta sauces, as mentioned above). The closer a food is to its natural state (e.g., an apple versus apple sauce versus apple pie), the healthier it will generally be.
Sugar Alcohols
Sugar alcohols are another type of carb used as sweeteners. They have half the calories of regular sugar, which means they also have fewer carbs. But that doesn’t mean all sugar alcohols are keto-friendly. For example, many sodas and alcohol drinks contain added sugar and sugar alcohol, which directly increase their calorie count.
Keto-Friendly Sugar Alternatives
Why do you eat sugar? The common answer will be to satisfy your sweet tooth. But you don’t need actual, high-carb sugar to do that. Seasoned keto dieters have learned to use keto-friendly sugar alternatives, including monk fruit, stevia, and allulose, which are all-natural sugar-free substitutes.
There are several keto-friendly natural sweeteners on the market, like stevia, erythritol, and monk fruit. Many of these sweeteners are good for baking and for sweetening up your morning cup of coffee. Keep in mind, though, that baked goods and other treats can still contain carbohydrates and are fairly processed. While they might seem like healthier choices, check the ingredient list.
Honey vs. Sugar on Keto
Since sugar is a high-glycemic carbohydrate, it’s usually one of the first ingredients to go. When it comes to sweeteners and the keto diet, it's important to understand the basic types of sugar we encounter in everyday foods. Sucrose, more commonly known as table sugar, is a compound made of both glucose and fructose. Because the keto diet relies on severely limiting carbohydrates, these sugars especially when refined or concentrated can disrupt ketosis.
Honey is often admired for its natural origin and nutrient content, including trace vitamins, minerals, and unique compounds like MGO (methylglyoxal) found in Manuka honey. That’s because honey, while natural, still contains sugars in the form of glucose and fructose. Honey generally has a glycemic index of around 55, while sugar is around 68.
From a keto standpoint, both honey and sugar can raise blood glucose levels and impact ketosis. That said, not all keto approaches are the same. Some individuals follow targeted or cyclical keto diets, which allow for more flexibility in carbohydrate intake. While both contain carbs, some individuals on flexible keto plans may substitute small amounts of honey in recipes.
Ultimately, it comes down to understanding your body’s response and your specific keto goals. However, for those aiming to strictly limit carbs, several keto-friendly alternatives offer sweetness without significantly affecting blood sugar levels. Popular low-carb sweeteners include stevia, erythritol, and monk fruit extract.
Using Alternatives Wisely
There’s no one-size-fits-all approach. You might consider adding a pinch of your preferred alternative sweetener to a chilled beverage, a no-bake snack, or a warm drink after it has cooled slightly. Many people prefer honey for its natural origin, trace nutrients, and rich flavor. Both honey and sugar offer sweetness, but their nutritional profiles are far from identical. For those following a ketogenic or low-carb lifestyle, the right option depends on your individual goals, carb tolerance, and preferences. At the end of the day, it’s about finding what works for your body and your routine.
The Benefits of Cutting Sugar
Nutritionists say that ideally, sugar intake for keto dieters should be 0 grams. But every person tolerates carbs differently. Depending on your carb allowance and diet goals, you may be able to consume small amounts of sugar, ideally from low-carb and nutrient-rich sources.
Cutting your sugar intake, even if you’re simply following a low-calorie or low-carbohydrate diet, has plenty of benefits. In a keto diet, it’s a must. Fortunately, there are quite a few benefits to cutting back (or cutting out) sugar.
- Improved Weight Management: Sugar is linked to weight gain. Cutting back on sugar will almost certainly result in weight loss.
- Better Blood Sugar: If you are managing conditions like diabetes, then reducing sugar intake can help you feel good and keep your blood glucose levels consistent.
- Lower Risk of Heart Disease: Sugar is linked to an increased risk of heart disease. If you want to improve cardiovascular health, ditch the sweets.
- Enhanced Dental Health: Your dentist wasn’t lying to you. Sugar plays a big role in tooth decay. Less sugar improves dental health and lowers your risk of cavities.
- Lower Risk of Certain Types of Cancer: While studies are still looking at the connection between high-sugar diets, inflammation, and cancer, there appears to be a correlation.
- Boosting Energy Levels: You’d think that sugar would give you more energy (and it does at first), but if your energy levels are unstable, cutting sugar can help you stabilize and keep your energy levels more evenly paced.
Tips for Managing Sugar Cravings on Keto
Many keto dieters will tell you that the keto diet isn’t that restrictive. You get to eat all the savory meats and snacks you want. But sugar cravings are a whole different story. But don’t reach for table sugar to curb them just yet.
When you start keto, your sugar cravings will likely subside within a few days. But of course, they can return when you see a yummy-looking dessert on a commercial or a big carbohydrate-heavy meal (that looks and smells delicious). Some people even experience “keto flu,” which refers to the headaches, cramps and fatigue that can develop and last for around a week.
Going cold turkey may prove ineffective in the long run, as it can reduce motivation once sugar cravings start to occur. Alternatively, choosing the right kind of sugar to consume is a great way to avoid completely cutting it out.
Here are some strategies to help you manage sugar cravings and stay on track:
- Utilize Keto-Friendly Sweeteners: There are several keto-friendly natural sweeteners on the market, like stevia, erythritol, and monk fruit. Many of these sweeteners are good for baking and for sweetening up your morning cup of coffee.
- Become a Label Reader: Nutrition labels are your best tool for tracking carbohydrates. Measure your foods and write down your carb intake, especially at first. Many people are surprised that what they thought was a portion size or serving was way off. They might assume that an item is made with whole grains and other healthy ingredients only has small amounts of sugar.
- Embrace Whole Foods: Enjoy foods as close to their natural state as possible. Berries are relatively low in carbohydrates but still taste like sweet snacks and are a healthy choice. For dessert, enjoy them with some whipped heavy cream.
- Modify Recipes: If you crave carbohydrates and sugar-heavy foods, consider ways to modify the recipe in a keto-friendly way. For example, avocado mousse or chia seed pudding sweetened with cinnamon.
- Avoid Deprivation: This brings us to our next point-don’t deprive yourself. If you're following keto, let go of the idea that you can't have full-fat cheese, cream, or bacon! Those are the benefits of a keto-friendly diet. The more you tell yourself that you can't have something, the more it feels like punishment.
- Find Keto-Friendly Alternatives: What is the secret to success on a keto diet? Learning to remake the foods that you love in a keto-friendly way.
Recent Research on Ketogenic Diets and Sugar Restriction
Study: Ketogenic diet but not free-sugar restriction alters glucose tolerance, lipid metabolism, peripheral tissue phenotype, and gut microbiome: RCT. Many modern and natural sweet foods contain free sugars like glucose and fructose. However, this approach has not been shown to reduce fat mass.
The ketogenic diet involves reducing carbohydrate intake for weight loss and altering one’s metabolism. Previous studies suggest that the ketogenic diet reduces physical activity energy expenditure (PAEE) levels compared to high-carbohydrate diets. Energy metabolism in skeletal muscle and fatty tissue can be affected by physical activity and nutrition. The gut microbiome, which produces short-chain fatty acids (SCFAs), also contributes to the regulatory inputs of these peripheral tissues on fasting and postprandial metabolism.
The researchers of the current study 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.
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.
The study findings emphasize that low carbohydrate or free sugar intake preserves PAEE in healthy adults. Reducing free sugar intake by 1% caused self-reported energy intake to decrease by 14 kcal/day, corroborating previous research. In the current study, 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.