If you’ve ever tried to lose weight, then you’re probably familiar with the “calories in, calories out” (CICO) equation.

Even though this concept seems pretty straightforward — eat fewer calories, lose more weight — many health experts argue that the CICO approach to weight loss is too simplistic and doesn’t account for the multiple factors that influence a person’s weight (1).

This article covers the CICO diet and explains whether it’s effective for weight loss.

A person goes running on a track outdoors.Share on Pinterest
RyanJLane/Getty Images

CICO is an acronym for “calories in, calories out.”

It’s not a specific diet. Rather, it’s the concept that creating a calorie deficit — by consuming fewer calories than you burn on a daily basis — leads to weight loss, while eating more calories than you burn causes weight gain (2).

That means weight loss and weight gain are determined solely by calorie intake, independent of macronutrient intake or diet quality.

Most weight loss diets are designed to create a calorie deficit, some more severe than others. But most popular diets recommend following a certain macronutrient ratio and cutting out specific foods and ingredients, such as added sugar, in addition to creating a calorie deficit.

However, using the CICO concept, the only factor that matters for weight loss is consuming fewer calories than you burn.

For example, according to the CICO theory, a person will lose the same amount of weight when following a ketogenic (keto) diet as they would when following a high carb diet, so long as the calorie deficit is the same.

How does the CICO diet work?

If someone is using the CICO method to promote weight loss, it basically means that they’re counting calories in order to stay within a calorie deficit.

To maintain a calorie deficit, you need to determine your energy needs.

You’ll need to calculate your basal metabolic rate (BMR) — the calories needed for basic physiologic functions such as your heartbeat and breathing — plus the calories used for digestion and physical activity.

While most people use online calculators to determine their energy needs, these tools are far from perfect and can provide only a very rough estimate of calorie needs.

Once you know your energy needs (or “calories out”), you must subtract calories from that number in order to promote weight loss.

For example, a person who needs 2,300 calories per day to maintain their current weight would need to consume fewer than 2,300 calories per day to promote weight loss.


CICO is the concept that creating a calorie deficit by consuming fewer calories than you burn leads to weight loss, while eating more calories than you burn leads to weight gain. It doesn’t consider factors like diet quality or macronutrient composition.

It’s true that calorie intake relative to energy expenditure is the most important factor in determining weight gain and weight loss.

Creating a calorie deficit, either by consuming fewer calories or by burning more calories through increased activity levels, will lead to weight loss (2).

There’s no arguing this.

A person can theoretically lose weight while eating a diet composed of highly refined products such as fast food just as they can lose weight following a nutrient-dense diet rich in health-promoting foods such as fruits and vegetables.

Many studies have shown that, when it comes to weight loss, it doesn’t really matter what kind of diet you follow, as long as you maintain a calorie deficit.

For example, numerous randomized control trials — considered the gold standard for establishing causal relationships — have shown that people can effectively lose weight on both low fat and low carb diets that create a calorie deficit (3, 4).

However, even though the CICO theory is correct, it’s not the only factor that matters for successful weight loss.

Successful weight loss and healthy weight maintenance depend on much more than creating a calorie deficit. Plus, the CICO theory applies only to weight loss and does not consider other aspects of health.

For example, CICO doesn’t consider diets’ role in hunger and satiety (fullness) or how a diet might influence disease risk (5).


Consuming fewer calories that you burn each day will result in weight loss. However, calorie reduction is not the only factor that matters when it comes to weight loss and maintaining a healthy body weight.

Eating within a calorie deficit will promote weight loss, which can benefit health for many people in a number of ways.

Excess body fat can significantly increase the risk of developing some health conditions, including heart disease, sleep apnea, depression, certain cancers, and respiratory conditions (6, 7).

Losing body fat by eating within a calorie deficit can help reduce those risks and improve mobility and overall quality of life for many people.

However, even though counting calories and eating within a calorie deficit may reduce body weight and improve certain aspects of health in many people with overweight or obesity, there are major downsides to focusing solely on calorie intake.

As mentioned above, CICO doesn’t take into account how food impacts health or how a food influences hunger or satiety.

For example, a meal of a doughnut and coffee with sugar is much less filling than a meal of eggs, berries, and avocado. That’s because the first meal is low in protein and fiber — nutrients that play important roles in appetite regulation.

Choosing foods high in fiber and protein helps improve satiety and may help you consume fewer overall calories, which can make it easier to maintain a healthy body weight (8, 9).

Additionally, CICO fails to recognize the importance of food beyond its calorie content. The foods you choose to eat provide the protein, fat, carbs, vitamins, minerals, and beneficial plant compounds your body needs to maintain optimal health.

Could you lose weight while following a diet consisting of only ultra-processed foods such as cookies and sugary cereal? Sure.

Is it the best diet for overall health and disease prevention? Absolutely not.

Research shows that dietary patterns high in ultra-processed foods increase the risk of developing a number of health conditions, such as type 2 diabetes, heart disease, and certain cancers (10, 11, 12, 13).

Conversely, diets high in whole, nutrient-dense foods such as fruits and vegetables protect against disease and are associated with longer life spans (10, 11, 12, 13).

That’s why it’s essential to choose foods based on their nutrient content and not just their calorie count. If you’re only concerned about calories and disregard how food choices may support or derail overall health, you’re missing the forest for the trees.

Additionally, tracking your food and calories — a common way dieters stay within a calorie deficit — can lead to a preoccupation with food and calories, which can promote disordered eating behaviors (14).


Trying to “do it right” when it comes to nutrition may feel tempting, but it can backfire. If you are preoccupied with food or your weight, feel guilt surrounding your food choices, or routinely engage in restrictive diets, consider reaching out for support. These behaviors may indicate a disordered relationship with food or an eating disorder.

Disordered eating and eating disorders can affect anyone, regardless of gender identity, race, age, socioeconomic status, or other identities.

They can be caused by any combination of biological, social, cultural, and environmental factors — not just by exposure to diet culture.

Feel empowered to talk with a qualified healthcare professional, such as a registered dietitian, if you’re struggling.

You can also chat, call, or text anonymously with trained volunteers at the National Eating Disorders Association helpline for free or explore the organization’s free and low cost resources.

Was this helpful?

CICO focuses only on calories and doesn’t consider nutrient quality, but food choices play an important role in weight management and disease prevention. Calorie counting can give way to disordered eating behaviors and preoccupation with food and dieting.

The CICO theory is pretty straightforward, but weight loss is not. Your body is a fantastically complex system that’s influenced by a number of factors both in and out of your control.

Weight loss is complicated, which is why taking an individual approach to weight loss is best.

If you feel that you want to or need to lose weight, you absolutely do not have to go on any diet, especially a diet that significantly cuts calories (like many popular weight loss diets) or involves tracking calories.

In fact, you can create a safe, healthy, and effective weight-loss-friendly diet without even thinking about calorie intake.

Here are a few tips for creating a healthy, sustainable dietary pattern that can help you lose weight without counting calories:

  • Choose foods based on nutrients, not calories. Rather than reach for low calorie foods such as rice cakes and egg whites, choose foods that pack in the most nutrients. Think fruits, vegetables, fatty fish, whole eggs, beans, and nuts.
  • Prioritize filling foods. Incorporating a source of protein and fiber at every meal can help you feel satisfied and may help decrease your overall calorie intake. Studies show that both high protein and high fiber diets are effective for weight loss (8, 9).
  • Stay active. It’s entirely possible to create a calorie deficit simply by increasing your daily energy expenditure. Try creating a fitness plan based on activities you enjoy.
  • Choose dietary patterns associated with healthy body weight. The Mediterranean diet, for example, has been shown to prevent unwanted weight gain and reduce the risk of developing a number of chronic diseases (15, 16).
  • Increase your produce consumption. Most fruits and vegetables are low in calories and high in fiber, vitamins, and minerals. Research shows that people who eat more produce tend to lose more weight than people who don’t eat produce regularly (17, 18, 19).
  • Have motivators unrelated to weight and appearance. For example, goals focusing on improving health markers such as physical fitness or cholesterol may help you be more successful than being motivated by weight loss alone (20).
  • Prioritize sleep and manage stress. Lack of sleep and chronic stress are both associated with weight gain. Getting enough sleep and taking steps to manage or reduce stress are important for weight management and overall health (21, 22).

Even though eating an appropriate number of calories and creating an energy deficit are essential to losing weight, they’re not the only habits that matter when it comes to reaching and maintaining a healthy weight.

Diet quality and composition, activity levels, sleep, and stress management matter as well — not just for weight loss but for the health of your entire body.

Your overall health — not your body size or weight — should always be your top priority. Diet culture messaging is pervasive, but we can and should feel empowered to focus on whole-body health.

If you need help creating a diet that prioritizes whole-body health, consider working with a knowledgeable registered dietitian, if you have access to one.


Even though creating an energy deficit is important when trying to lose weight, it’s not necessary to count calories or track your food intake. The tips listed above can help you develop a dietary pattern that prioritizes whole-body health.

CICO (“calories in, calories out”) is the concept that creating a calorie deficit by consuming fewer calories than you burn each day leads to weight loss, while eating more calories than you burn leads to weight gain.

Although creating a calorie deficit is essential for weight loss, the CICO method is overly simplistic and doesn’t consider factors such as diet quality and macronutrient content, which play an important role in weight maintenance and disease prevention.

Although following the CICO method will likely result in weight loss, at least temporarily, it’s best to create a weight-loss-friendly dietary pattern that considers other factors, such as diet quality and ability to reduce disease risk.

Just one thing

Try this today: If you’re following a diet that requires you to count every calorie and track every piece of food, it may be time to change your approach. Tracking calories this closely is unnecessary, and for some people, it can lead to disordered eating behaviors and significantly affect mental health.

If you’re not sure how to stop counting calories or tracking food, consider working with a registered dietitian or therapist who specializes in disordered eating behaviors.

Was this helpful?