Should you count calories on a low-carb or keto diet?

When it comes to weight, calories are often talked about but frequently misunderstood. Indeed, whether counting calories is actually useful for weight loss is debatable. Read on to learn about calories and their role in weight regulation on low-carb and keto diets.

What are calories?

A calorie is a unit of energy that your body uses to perform hundreds of tasks. These include voluntary movements like walking, running, and jumping, as well as involuntary ones like breathing, circulating blood throughout your system, and maintaining normal body temperature.

Your body needs a certain number of calories just to keep these involuntary processes going. This is referred to as your basal metabolic rate, or BMR. Your BMR is influenced by many factors, including your age, gender, body composition, and genetics.1

You require additional calories for physical activity, including walking. Overall, the more active you are, the more calories you’ll need.

How many calories do carbs, protein, and fat provide?

Each macronutrient provides a specific amount of calories:2

  • Carbs: 4 calories per gram
  • Protein: 4 calories per gram
  • Fat: 9 calories per gram
Importantly, even though fat provides more than twice as many calories as carbs,  you may have noticed that it’s much more filling.

Protein is generally considered the most satiating macronutrient, but it’s mostly used for cell repair and muscle maintenance.3 It’s not very effective as an energy source because it must first be converted to glucose in the liver in order to be used as fuel. Eating extremely high amounts of protein isn’t necessarily a good thing and may reduce the effect of a strict low-carb diet. Learn more

Pure fats (such as butter, ghee, and lard) and oils get 100% of their calories from fat. However, the calories in most foods are a combination of carbs, protein, and fat.

For instance, although eggs are considered a protein food, the majority of their calories actually come from fat. For example, two large eggs provide 146 calories:

  • 4 calories from carbs (1 gram) (2%)
  • 52 calories from protein (13 grams) (34%)
  • 90 calories from fat (10 grams) (64%)

Calories count, but they are not the whole story

Generally speaking, if you take in more calories than your body needs over a longer time period, the extra calories will be stored as fat. Similarly, if you take in fewer calories than needed over a longer time period, your body will release its fat stores, and you will lose weight.

However, there is far more to weight regulation than just monitoring calories in vs. calories out. Indeed, most members of the human race appear to have regulated their weight effectively for millennia, before anyone even knew what a calorie was.

The modern obesity epidemic seems to be an unprecedented phenomenon, and it coincides with an ever-increased focus on counting calories. Correlation is not causation, so it would be wrong to say that counting calories causes obesity. However, at best, counting calories seems to be an imperfect aid to weight control. So what is really going on? As it turns out, hormonal regulation is key.

Hormones play a large role in influencing appetite, fullness, and fat storage. Research suggests that low-carb and keto meals may trigger hormones that lead to a natural reduction in calorie intake, especially in those who are overweight or insulin resistant.4

In one study, overweight people consumed a breakfast of eggs or a bagel. Although each meal contained an identical amount of calories, the group that consumed the egg breakfast stayed full longer and ate fewer calories at lunch than the bagel group did.5

Additionally, your insulin level – and how sensitive your body is to insulin – will influence whether you store or burn calories. Researchers have shown that impaired insulin response following weight loss reduces metabolic rate and drives weight regain. However, lowering carb intake may help to counteract this effect.6

What’s more, when it comes to weight loss, low-carb diets regularly outperform low-calorie diets, even in studies where calories aren’t intentionally counted or restricted during low-carb eating.7

For example, in a 2004 study, overweight and obese adults consumed a low-fat diet and a low-carb diet for one week each. Both diets were designed to reduce each person’s calorie intake by 500 calories per day. Yet people lost more weight and body fat after the low-carb week than the low-fat week – even though men in the study averaged higher calorie intake during the low-carb phase.8

Clearly, calories are only one factor involved in weight regulation.

Video: Doctors answer

Dr. Eenfeldt: Isn’t weight loss all about calories?

Dr. Naiman: Yes, weight loss is all about… No, weigh loss is definitely not about calories. And I have a zillion patients who’ve gone on low calorie diets. And you can lose weight that way and you will immediately regain it. And we have plenty of studies that document this. So weight loss is not all about calories.

Dr. Eenfeldt: Isn’t weight loss all about calories?

Dr. Brukner: Well, so they’ve tried to convince us for the last 30 years. But calories in, calories out has been the philosophy of the 30 years. But, you know, you’re going to tell me that 100 cal from a piece of salmon is exactly the same as 100 cal from candy, or chocolate, or ice cream…

I mean that doesn’t make any sense at all, does it? So I mean calories in, calories out has been disproved. I mean there are calories from differences that have markedly different effects. And until we get rid of this whole calories in…

It’s been a disaster this calories in, calories out. I mean look at the effect. Since we have adopted that philosophy we have worldwide epidemics of obesity, diabetes, faKy liver and so on… It’s been a disaster and the sooner we forget about it… It’s sort of an attractive concept, you know, what you bring in, what you take out… But unfortunately it doesn’t work.

Dr. Eenfeldt: Isn’t weight loss all about calories?

Dr. Westman: Well, I think calories matter. The energy balance equation where we talk about energy in… calories in, calories out isn’t a good construct to help guide people… It’s more complicated than counting the calories on a label, for example.

Because the calories are handled differently depending on what type of calorie it is, based on the metabolism for that individual calorie. But I think that it’s pretty clear that when people are losing weight, they are eating fewer calories than they were before.

And then of course if the weight loss program that they are doing changes the metabolic rate, that’s another factor you have to take into account. But I think it’s fair to say that a low-carbohydrate diet isn’t magical. It follows the rules of science that we understand, having to do with energy balance and the calories.

So when I teach the low-carb diet, I don’t talk about calories. We don’t have to teach calories, but people are still eating fewer calories in general. That’s, you know, not the case for everyone. That’s the role for the practitioner to help people troubleshoot those situations.

More Q&A videos with doctors

Counting calories: yes or no?

At Diet Doctor, we don’t recommend counting calories. First of all, it’s impossible to know exactly how many calories you’re getting from a specific food, let alone precisely what your body will do with those calories. It’s far more important to choose foods that promote the release of hormones that reduce hunger, help keep you satisfied, and make it easier to achieve a healthy weight.

Focus on minimally processed foods that contain high-quality protein, healthy fat, and nutrient-dense fibrous carbs, especially vegetables.

And if you are really struggling to lose weight, stay away from high-calorie, high-reward foods that are easy to overindulge in, even if they are low in carbohydrates. Classic examples of such foods are cheese and nuts.

Rather than counting calories, make all of your calories count by eating nourishing, well-balanced low-carb meals.

Franziska Spritzler, RD

  1. Medicine and Science in Sports and Exercise 2015: Examining variations of resting metabolic rate of adults: a public health perspective [review of non-controlled trials; weak evidence]

  2. The Journal of Nutrition 1994: Atwater and USDA nutrition research and service: a prologue of the past century [overview article; ungraded]

  3. The American Journal of Clinical Nutrition 2008: Protein, weight management, and satiety [overview article; ungraded]

  4. PLoS One. 2018: A high carbohydrate, but not fat or protein meal attenuates postprandial ghrelin, PYY and GLP-1 responses in Chinese men [randomized crossover trial; moderate evidence]

    European Journal of Clinical Nutrition 2013: Ketosis and appetite-mediating nutrients and hormones after weight loss [non-randomized study; weak evidence]

  5. Journal of the American College of Nutrition 2005: Short-term effect of eggs on satiety in overweight and obese subjects [randomized crossover trial; moderate evidence]

  6. This has been shown in several high-quality trials:

    Obesity (Silver Spring) 2015: Relationship of insulin dynamics to body composition and resting energy expenditure following weight loss [randomized crossover trial; moderate evidence]

    Journal of the American Medical Association 2012: Effects of dietary composition during weight loss maintenance: a controlled feeding study [randomized crossover trial; moderate evidence]

    British Medical Journal 2018: Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial [randomized trial; moderate evidence]

  7. You can find a large number of such studies here:

    Low-carb weight loss studies

  8. Nutrition & Metabolism 2004: Comparison of energy-restricted very low-carbohydrate and low-fat diets on weight loss and body composition in overweight men and women [randomized crossover trial; moderate evidence]