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Before it became a “mainstream” diet and lifestyle, the ketogenic diet was (and still is) used to treat epilepsy in children. Now, it’s used for weight loss and a slew of other health-related conditions.

The ketogenic diet induces a state of ketosis, meaning blood levels of ketones are elevated. This occurs due to carbohydrate restriction, which causes the body to burn fat and from this, produce ketone bodies. Now, you can find keto products on shelves everywhere, ranging from keto cookies to keto protein powders, which can be consumed guilt-free on a ketogenic diet. Or can they?

Many advocates of keto claim that you don’t have to count calories on the diet. This is a bit of a simplistic conclusion. Just like refined and junk food can be over consumed, so too can so-called “healthy” keto-friendly foods and other keto-friendly products—the ketogenic diet probably just makes you less likely to overeat them. So, do calories matter on keto? Let’s take a look.

What are Calories?

While the term “calories” is associated with food, they’re actually a measurement of heat.

In technical terms, one calorie (kCal) is the amount of energy needed to heat one kilogram of water by one degree Celsius. Measuring energy in calories is a way that food scientists have developed to quantify the amount of energy present in foods.

Foods contain varying amounts of energy stored in their atomic bonds. When the bonds are broken down, this energy is released (as heat).

Each macronutrient—carbohydrates, protein, and fat—have different calorie contents due to the energy they contain.

For instance, one gram of protein and carbohydrate each contain four calories, while one gram of fat contains nine calories; this is called their physiological fuel value.

Are All Calories Created Equal?

Traditional weight loss models basically all follow the same “simple” premise—that weight is governed by the specific equation of calories in minus calories out. It’s the first law of thermodynamics: total energy in a system is constant, it can’t be created or destroyed, but only change “forms.”

Using this concept, the only thing you need to do to lose weight is consume less energy (reduce the “calories in” side of the equation) than you’re using (increase or maintain the “calories out”).

The “calories in calories out” model, also known as CICO for short, has many times failed to produce successful weight loss outcomes. This may be due to a couple of reasons.

The first may have to do with “calories in"; people are pretty bad at quantifying how much they eat, and even those who are meticulous about tracking calories will experience large errors inherent to all calorie counting methods. Simply put—we can’t for sure tell how many “calories” someone gets from a food.

The other flaw with CICO is that, as you reduce calories, resting energy expenditure drops. When you eat less, your metabolism begins to slow down. This is a compensatory mechanism, which tries to defend body weight (meaning, keep weight on to protect from starvation) by adapting metabolism.Woo1985

In the long term, this is why weight loss maintenance is difficult for some people.

This drop in metabolic rate will either halt weight loss (known as a “plateau”) or eventually lead to weight regain, unless calories are restricted further. A vicious cycle precipitates.

For instance, one study placed obese participants on several different diets and observed that resting metabolic rate (RMR) decreased after three months of a calorie restricted (CR) diet (25% energy restriction). Participants on a low-calorie diet (890kcal/day) and those on a calorie restricted + exercise regimen also had slower metabolisms at week six.Martin2007 Interestingly, however, resting metabolic rate may be preserved during weight loss if fat free mass is also preserved as seen in one study.Connolly1999

However, the participants in this study had, on average, only a 250 - 380kcal decrease in daily calories instead of the more drastic isocaloric diets people tend to experiment with, which may also explain the lack of a decrease in RMR. They also ate significantly more fiber and had greater insulin sensitivity, which may also explain the lack of a change in RMR.

RMR may also be maintained during weight loss on a higher protein / lower carbohydrate diet. When compared to other diets (high-carbohydrate), low-fat and high-protein intake seems to have the least effect on reducing RMR during reduced calorie intake.Ebbeling2012

The CICO model also disregards one crucial factor—it treats all calories equal, and this is not the case.

A calorie from protein is not the same as a calorie from fat, and is not the same as a calorie from carbohydrate. Different foods have indirect effects on energy “intake” and “output” because they require different amounts of energy to process and store. This concept is known as the “thermic effect of food” (TEF). As a result, the composition of your diet will influence energy balance.

There have been various studies that have investigated the TEF of food. Most of these involve manipulating the composition of fats, protein, and carbs in meals and have found that meals higher in protein result in an increase in resting energy expenditure.Westerterp2004

This translates to higher energy expenditure on a diet that’s low in carbohydrates while higher in protein (and fat).

Studies have shown that a diet containing a high protein intake created twice the energy expenditure compared to a high-carbohydrate diet, low-fat diet.Johnston2002 Resting energy expenditure was measured 2.5 hours after each meal. Body temperature was, not surprisingly, also higher, which could partially explain this difference in energy expenditure.

All this is to say that dietary composition can drastically change the way calories are used by the body, altering resting metabolic rate and the thermic effect of food. On top of physical activity, these three factors contribute to our overall energy expenditure (how many calories we use).

In summary, to claim that “a calorie is a calorie” defies a few well-known thermodynamic laws. Some suggest that this idea is best headed to it’s grave.Feinman2004

A pie chart showing how the body uses calories

How Macronutrients Affect Hormones

The thermic effect of food isn’t the only variable that is different among carbs, protein, and fat.

Calories aren’t the only thing that determine weight loss. Hormones play a profound role in telling your body what to do with the calories you eat.

The hormonal “big three” when it comes to weight loss are insulin, glucagon, and leptin.

Insulin is perhaps the most well-known of these. When blood sugar rises, insulin is released by the pancreatic beta-cells in order to regulate blood glucose levels. It does this by shuttling glucose into cells (like skeletal muscle tissue) where it’s either used as a fuel source or stored as muscle glycogen.

Insulin is sometimes called the “fat storage hormone” because it promotes fat synthesis / storage, and also suppresses fat breakdown (lipolysis). Basically, insulin is a signal that tells the body there is plenty of fuel around (usually glucose), so fat stores don’t need to be called upon.Jensen1989

What is a big trigger for insulin levels to rise? High carbohydrate foods.

Glucagon is the “counter hormone” to insulin—it’s released when blood glucose levels are low (and hence insulin is too). Glucagon release is a trigger for the liver to begin releasing stored glucose (glycogen) in order to maintain homeostasis.Jiang2003 This can be invaluable between meals, during exercise, or any other time glucagon is released, like during “fight or flight” situations.

On low-carbohydrate diets, glycogen will be low, and thus, when glucagon is released, it “searches” for other sources of fuel. In this case, glucagon will lead to the release of triglycerides from fat tissue, which are then broken down into free fatty acids and sent off to the liver to be used in the production of ketone bodies.Keller1983

Leptin is a hormone produced by adipocytes (fat cells) and is commonly known as the “satiety hormone.” Leptin signals to the body and brain that there is adequate fuel around, so there’s no need to eat. While only slightly related, leptin resistance occurs in some forms of obesity—the signal stops working. Kelesidis2010

Leptin is a signal that “senses” nutrients—calories in, calories out, and how many “calories” we have stored as fat.

Having enough stored fat, or even fat from dietary sources, can cause leptin to be highly active, leading to satiety.Friedman1998

Some have proposed that rather than inhibiting food intake, leptin might actually only serve as an “emergency signal of energy depletion” when levels are low. Low leptin or leptin that falls below an individual’s “set point” (that occurs in weight loss, for instance) can promote hunger and weight gain. Either way, having leptin around seems to regulate appetite.

Interestingly, ketogenic diets have been shown to increase serum leptin levels and maintain leptin sensitivity, likely due to the high fat content of the diet.Thio2012

The concept that different types of foods can impact how much we eat, regardless of the mechanism, was illustrated in a recently published and well-controlled diet study.

When two diets containing unprocessed and ultra-processed foods were compared side-by-side over 28 days, the ultra-processed diet (containing little-to-no whole foods) caused participants to eat an extra 500 calories per day. Rather than suppressed, appetites seemed to be enhanced when low-quality food was consumed.Hall2019 Strike three for junk food.

An illustration of a nutrition label in hieroglyphics, showing that nutrition labels can be extremely confusing

Ketogenic Diets and Weight Loss

Let’s defy scientific practice for a minute and skip to the results section first. Ketogenic diets seem to be better for weight loss and weight loss maintenance in the long term.

In a meta-analysis of 13 diet studies, individuals who were assigned to a very-low carbohydrate ketogenic diet (<50g carbohydrates/day) had significantly more body weight loss (about 1kg on average) in the long term compared to conventional low-fat diets.Bueno2013

Another analysis, this one including 17 different randomized controlled trials, found evidence that diets with a low-carb intake were associated with significantly greater weight loss compared to low-fat diets.Sacknerbernstein2015

A one-year trial compared a diet that induced nutritional ketosis (i.e. ketogenic diet) to a “usual care” intervention in type 2 diabetic patients. It demonstrated that the ketogenic diet intervention was better at reducing weight (by about 14 kilograms) along with improving blood glucose control better than usual care.Hallberg2018

Where does the weight loss come from? Some claim that “it’s all water weight,” but this may only be true initially. In the long term, fat loss may be a substantial portion.

For instance, in one study, weight loss after 15 days on a ketogenic diet was due to total body water (about 2.3 kilograms). After this time point, however, a slight recovery of body water was observed. Water loss may occur due to glycogen depletion. Glycogen is usually stored with water, and so a loss of glycogen means water will come along with it, along with some ketones and sodium.Gomezarbelaez2017

In the long term, however, evidence says that most of the weight lost on a ketogenic diet comes from fat, while fat-free mass is probably maintained. Studies have shown that carbohydrate-restricted diets conducted over several weeks lead to reduced body fat mass and maintained, or even increased, lean body mass.Volek2002,Willi1998

The Metabolic Advantage of Ketogenic Diets

To claim that “a calorie is a calorie” would require that two diets containing an identical amount of calories could not lead to different amounts of weight loss. This has been shown to be false.

When matched for calories, low-carbohydrate diets (higher fat and protein intake) have a “metabolic advantage” compared to low-fat high-carbohydrate diets.Feinman2004 What this means is that for the same amount of calories, low-carb diets result in a greater amount of weight loss compared to high-carb diets. This is probably due to their thermodynamic effect.Feinman2007

The studies showing superior weight loss on ketogenic compared to low-fat diets support this claim, as do trials that measure basal metabolic rate (BMR). Low-carb diets might increase energy expenditure by 100 - 500 calories per day.Hall2016

The additional thermic effect of food means that an increased energy expenditure will result in more calories burned, and thus more weight loss in the long term.

Better weight loss probably results from several factors. The first is the high thermic effect of protein. Protein takes more energy to metabolize compared to carbohydrates and fat.

However, some keto advocates advise not consuming too much protein while on keto.

Second, a process called gluconeogenesis (GNG) requires energy. When carbohydrate intake is low (and so are glucose and glycogen), the body uses amino acids (from protein breakdown) to create glucose that’s needed by certain body tissues and cells like red blood cells and certain parts of the eye.

GNG is energetically costly—it’s estimated that around 400 - 600 extra calories per day may be required for GNG to occur (for instance, in someone on a ketogenic diet).Paoli2013

Keto adaptation also increases the rate of fat-burning compared to other diets.Volek2016 Low insulin levels trigger the breakdown of triacylglycerols (TAGs) in fat into free fatty acids. Low insulin also inhibits fat storage.Feinman2007,Volek2016

There’s also the well-known concept that lean mass requires more calories to “maintain” than does fat tissue. Therefore, increasing lean body mass (in the form of muscle) on a ketogenic or low-carb diet can also help to increase your resting metabolic rate.

Not to beat a dead horse, but all of the above statements are supported by the fact that a consistent metabolic advantage (i.e.more weight loss) is seen for low-carb diets in the literature.Feinman2007,Feinman2004,Manninen2004

Picture of Lettuce Next to a Skillet Filled with an Omelette

Appetite Suppression

One reason that some people seem to struggle with long-term weight loss and maintaining weight loss when using “traditional” calorie restricted diets is simple...they get hungry!

Long-term calorie restriction has been called “unfeasible” by many, or otherwise just plain miserable by others. A weight loss regimen is only effective if you can stick to it—hence the failure of many approaches that leave dieters feeling hungry and unsatisfied, just like dinner at an overpriced restaurant.

One of the most touted, research-backed aspects of the ketogenic diet is appetite suppression, which some refer to as “satiation” (basically, the condition of “feeling full” and satisfied).

A common "symptom" of ketogenic diets is that they seem to be superior to other diets in terms of regulating hunger.

This is probably due to the macronutrient composition of keto diets—they’re high in fat and moderate in protein, which are claimed to be more satiating nutrients than carbohydrates. You can sometimes see this for yourself after eating a high-protein high fat meal. You might not feel like eating for a bit. Contrast this with a big bowl of late-night cereal, which leaves you craving even more.

It might not be just a feeling of stomach satisfaction mediating this effect.

Ketosis has been shown to suppress ghrelin, which is often known as the “hunger hormone.”Sumithran2013,Johnstone2008,Stubbs2018 Ketones are thought to act as signaling molecules in the body which might have many effects, one of which is to tell the brain, “Hey, we’re full.”

This effect may be seen with either endogenous or exogenous ketosis.

For instance, an analysis of trials on ketogenic diets showed that individuals on these diets experienced less hunger and a reduced desire to eat, even while they were restricting calories to lose weight.Giibson2015 For some, this is an unexpected finding, since a common symptom of chronic calorie restriction is complaints of hunger. This didn’t seem to happen on ketogenic diets.

In addition, the BHB monoester that’s found in many exogenous ketone ester supplement are shown to suppress appetite by lowering ghrelin.Stubbs2018 While exogenous ketosis doesn’t confer the weight-loss benefits that endogenous ketosis does, this appetite suppressant effect of ketone supplements could come in handy during an extended fast, or to curb hunger if you are trying to calorie restrict.

Along with exogenous ketone supplements, you can also leverage medium-chain triglycerides (MCTs) to help reduce hunger. MCTs are highly ketogenic fats, meaning they’re readily converted into ketones despite not being ketones themselves. You can mix them right into your morning coffee to help help keep the hunger at bay until the late afternoon.

The ability to go long periods of time without hunger and control appetite (rather than let your appetite control you) can be an empowering feeling.

If you’re trying to lose weight or are just looking for a way to remove constant cravings of food throughout the day, eating a keto diet or using exogenous ketones might be a great place to start.

As a result of feeling more satisfied after meals, ketogenic diets might promote a decreased caloric intake as well, if that’s your goal.

An illustration of the human body showing how keto helps weight loss

Should You Count Calories on Keto?

First of all, one important thing to realize is that calorie counting is inherently a flawed process. There are two reasons for this, which we’ve touched upon.

The first is that, it’s virtually impossible to know exactly how many calories you’re deriving from a food. Digestion, nutrient partitioning, and other factors make this calculation a rough estimate, at best.

Second, the calorie counts for many foods, including produce, will all be different depending on the database you use and where you buy them. The above factors introduce a lot of error into the accurate estimation of caloric “intake.” While you can get a good ballpark idea of your food quantity consumed, take it all with a grain of salt.

So, should you do count calories on keto? Well, this depends.

Initially, counting the number of calories you’re consuming while on keto might be a good thing to do, just to get a general idea of how much you’re eating. “Keto foods” (especially packaged products) are inherently high in fat, making them quite calorically dense and easy to overdo, if you’re not careful; you definitely don’t want to increase your daily caloric intake significantly by eating more fat than you need.

Despite what many people say, it is possible to overdo your protein and fat intake. If you’ve ever found it tempting to throw down an entire jar of peanut butter, you understand our sentiment.

Overdoing it on oils, nuts, butter, even the “healthy fat” sources like olive oil and avocado—this could lead to an increased calorie consumption. The only caveat is that while eating keto, you’ll just be less likely to overdo it.

For an example, let’s take a look at the energy content of some commonly-consumed keto-approved foods. This isn’t to say these foods are bad, but rather than their high caloric density but low physical volume could make them easy to binge on. You might want to make your meal plan less dense in these foods.

Let’s start with cheese, a weakness of many.

One ounce of typical cheese like cheddar or gouda contains about 100 calories, 7g of protein, and 9g of fat. Sure it’s low carb, but bingeing out on a 10oz cheese ball can run you 1,000 calories or more.

Butter and cream are easy ways to get some extra fat into your ketogenic diet, since they can be pretty much be added to any dish. But 1tbsp of butter has 100 calories, and a tbsp of cream has 50. Coconut oil, another popular fat used for cooking and mixing into dishes, has 120 calories per tbsp.

If you’re cooking everything you eat in coconut oil, mixing butter into your coffee, and fitting daily cheese snacks into your diet, this could be a quick way to unknowingly overdo it on your energy intake. This easy to is avoid by being aware of how much you’re eating. Eat mindfully, not mindlessly.

Another easy way to “count” your calories might be to simply observe yourself...or the scale. Maybe you’re not getting the weight loss results you expected, despite being in ketosis a majority of the time. This could be due to the fact that you’re eating too many calories, mostly in the form of fat.

Sure, you’re burning more fat, but a lot of this could be coming from that fat you’re eating, not body fat. In this case, your body fat percentage may change little. While it’s more complex than it sounds, when it comes down to it, weight loss generally requires a calorie deficit, rather than a caloric excess.

You don’t hear of many keto weight gain stories, but they’re out there. However, most likely, strict caloric control or monitoring of calories isn’t necessary. Your resting metabolic rate might also increase due to the lower-carb and higher-protein nature of a ketogenic diet. By promoting satiety, blood sugar control, reducing cravings, and boosting metabolism, high-fat diets are pretty good at self-regulation.

Make Calories Count

If you’re hungry, eat. If you’re not, don’t.

Many people have adopted this way of thinking and experienced life-changing results in response. Everyone loves food, but nobody wants it to control their lives.

Ketogenic diets comprised of whole foods that are high in fat and protein can eliminate the obsessive calorie counting once (and still) espoused by many a dietitian and health practitioner. These results will vary by user, but an overall trend toward success and a healthier life with ketogenic diets is becoming clear.

Overall, keto is about prioritizing quality over quantity, and the results often speak for themselves.

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