The CICO Diet: The Calories In Calories Out Method To Weight Loss

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We’ve long been told that weight loss is simple: it’s a matter of calories in versus calories out. 

In other words, if you consume fewer calories than you burn in a day, you will lose weight, and if you eat more calories than you burn, you will gain weight.

In this way, many health experts argue that counting calories is the only route to weight loss because it ensures you’re keeping the “calorie equation” as a calorie inequality such that you’re maintaining a caloric deficit.

This very concept is the premise behind the CICO diet, which stands for “calories in, calories out.” But, is the calories in, calories out equation too simplistic? Does the CICO diet work? Can you lose weight on the CICO diet?

In this article, we will discuss the CICO diet, whether calorie counting works for weight loss, and how to follow the CICO diet if you’re trying to lose weight.

We will cover: 

  • What Is the CICO Diet?
  • What Can You Eat On the CICO Diet?
  • How to Do the CICO Diet
  • How Do You Determine Calories In, Calories Out?
  • Does the CICO Diet Work?
  • Pros and Cons of the CICO Diet

Let’s get started!

A variety of food with their calorie number on them.

What Is the CICO Diet?

The CICO diet stands for “calories in, calories out,” referring to the popular theory that changes in your weight in either direction are solely dependent on the state of caloric balance or caloric imbalance that you are in.

When you are in a state of caloric balance or energy balance, you are consuming the same number of calories per day as you are expending.

Caloric imbalance can either be a caloric deficit, in that you’re burning more calories than you’re consuming, or a caloric surplus, in that you’re consuming more calories than you’re burning.

The CICO diet is based on the theory that a caloric deficit leads to weight loss.

The CICO diet differs from popular diets like the paleo diet, Whole30, the vegan diet, or the ketogenic diet in that there aren’t specific guidelines about foods you can eat and foods you cannot eat.

A post-it that says counting calories, a calculator, and a variety of foods.

Instead, the CICO diet is based entirely on calorie counting, such that so long as you are consistently generating a caloric deficit by consuming fewer calories than you burn in a day, you will lose weight.

There are zero stipulations about what you eat or don’t eat, so the quality of your diet and the macronutrient ratio is not regulated.

Although nearly all popular diets that are at least marginally effective rely on creating a caloric deficit, most of these diets provide some type of macronutrient ratio to follow or have other recommended foods to eat or foods that are off-limits.

For example, on the ketogenic diet, you severely restrict your carbohydrate intake. On a low-fat diet, you limit the amount of dietary fat you consume, often resulting in a high carbohydrate intake.

In their own ways, both of these diets are based on the shared premise that limiting a certain macronutrient (carbohydrates in the case of keto and fat in the low-fat diet approach) will result in weight loss.

In contrast, the CICO diet is based solely on your state of caloric balance: if you’re eating fewer calories than you burn, you’ll lose weight. 

Therefore, if you believe the theory behind “calorie math,” whether you follow a keto way of eating or a low-fat diet, your weight loss results would be identical if the calorie intake was the same in both approaches.

A person holding a donut and their phone with a calorie app open.

What Can You Eat On the CICO Diet?

As mentioned, you can eat whatever you want on the CICO diet. There are no particular foods that are recommended, nor are there any excluded foods.

Of course, many medical and nutrition professionals would argue that the quality of your diet will not only impact your health but also your weight loss.

How to Do the CICO Diet

There’s really only one “rule” with the CICO diet: count your calories.

If you are trying to lose weight, you have to consume fewer calories than you burn. If you are trying to maintain your weight, you need to be an energy balance. If you are trying to gain weight, you need to consume more calories than you burn.

When it comes to the number of calories you burn in a day, it’s important to remember that this number includes more than just the calories you burn during exercise. 

Total daily caloric expenditure is the sum of your basal metabolic rate (BMR), the physical activity you do in a day for general activities (working, cooking, hygiene, etc.), deliberate exercise, and diet-induced thermogenesis, which refers to the calories you expend digesting the food you eat.

The American Council on Exercise reports that your BMR represents about 60-75% of the total calories you burn in a day, though it depends somewhat on your physical activity level.

The more active you are—both with planned exercise and accumulated physical activity going about your day—the smaller the overall contribution your BMR will have on your total daily caloric expenditure.

The calories you burn during deliberate exercise and physical activity as you go about your day depend on how active you are but usually constitute about 30% of your daily caloric expenditure.

The remaining factor that affects how many calories you burn in a day, diet-induced thermogenesis, also called the thermic effect of food, typically constitutes about 5 to 15% of your daily caloric expenditure.

Evidence suggests that diets high in protein and alcohol increase diet-induced thermogenesis, whereas diets high in fat have the opposite effect.

A person eating a salad looking at their calorie app.

How Do You Determine Calories In, Calories Out?

In terms of the caloric intake side of the equation, it’s fairly easy to calculate how many calories you consume by measuring portion sizes and then using the nutrition facts on the food label or online in various diet apps.

The caloric expenditure side of the equation can be a little more complicated. If you wear a fitness watch or activity monitor that records your heart rate over the course of the day, you can get a fairly accurate estimate of your daily energy expenditure.

Alternatively, you can estimate your BMR or even your entire daily caloric expenditure with online calculators

This method is not as accurate as the data you will get from a heart rate monitor, but it’s a good starting place.

A person on the CICO diet writing down their calorie intake.

Does the CICO Diet Work?

The CICO diet can work because generating a consistent calorie deficit, either by consuming fewer calories than you burn or by burning more calories than you consume, can lead to weight loss

Furthermore, although debated within the nutrition community, there is evidence to suggest that the macronutrient ratio of your diet doesn’t really matter as long as you’re in a caloric deficit. 

For example, studies have shown that both low-fat and low-carbohydrate diets can be effective means of losing weight.

However, the CICO diet doesn’t consider the quality of your diet, and this is a major shortcoming.

A plate of food and a person noting down their diet plan.

Pros and Cons of the CICO Diet

In many ways, the primary benefit of the CICO diet compared to other diets—the fact that you have maximum flexibility to eat whatever you want—is also the primary drawback.

By not providing any stipulations on what you can eat, the CICO diet has the potential to be very unhealthy.

You can follow the CICO diet by restricting your calories every day but may be only eating processed foods like chips, candies, and snack cakes.

Of course, diet quality has a huge impact on your health and how your body feels and performs.

It’s possible to follow the CICO diet and have major nutritional deficiencies, depending on your food choices. In this way, the CICO diet can increase the risk of certain diseases such as diabetes, obesity, and hypertension.

For instance, a diet consisting of lots of simple sugars, such as those found in soda, cookies, and white bread, can lead to insulin resistance, while a diet high in processed meats, chips, and canned soups can lead to hypertension.

A calorie counting app.

Additionally, the CICO diet also fails to consider any other factors that can contribute to weight loss or weight gain such as the satiety of the food you eat, the effect on blood sugar and insulin, the impact of your diet on the composition of your gut microbiome, and your hormonal profile.

According to the International Society of Sports Nutrition’s position stand on diets and body composition, the CICO diet oversimplifies how weight loss occurs in practice, even if calories in, calories out makes sense in theory.

This position stand cites the importance of factors that regulate appetite, such as food quality, sleep, and physical activity.

For example, foods high in fiber, protein, and healthy fats will leave you feeling fuller for much longer than foods high in “empty calories,” like simple sugars and hydrogenated fats.

Another important shortcoming discussed is the difference in the thermic effect of the different macronutrients. 

Studies show that the thermic effect of protein is 25–30% in terms of the percentage of the energy content. 

A person preparing a shake.

For example, if you eat 100 calories of protein, 25-30 calories are burned right away just by digesting the food, leaving a net caloric gain of only 70-75 calories from that food.

In contrast, the thermic effect of carbohydrates is 6–8%, and that of fat is 2–3%.

With this in mind, what you eat can matter, even just within the context of your caloric balance.

It’s also somewhat difficult to accurately estimate the number of calories you burn in a day. If you overestimate, your CICO diet weight loss results might not be as impressive as you’d expect

In most cases, the CICO diet can help you lose weight if you’re accurate with your calorie accounting and maintain a consistent caloric deficit.

However, the quality of your diet is extremely important for your overall health, and it can also impact your weight loss results.

For this reason, it’s usually best to focus on eating a nutritious, nourishing diet with satiating foods more so that the exact number of calories you’re eating and burning.

Check out our guide to the three top popular healthy diets for some guidance on healthy eating.

A person holding a phone with a calorie counting app open.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

1 thought on “The CICO Diet: The Calories In Calories Out Method To Weight Loss”

  1. Nice Amber. Yes, you are right. I agree with you saying that “We’ve long been told that weight loss is simple: it’s a matter of calories in versus calories out. In other words, if you consume fewer calories than you burn in a day, you will lose weight, and if you eat more calories than you burn, you will gain weight.” Your article is very helpful. Thank you Amber!


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