The CICO diet is a simple concept of "calories in, calories out." The idea has been around for ages. But its nickname, CICO, is new. It's an easy way to lose weight in the short term.
“It’s simple science: if you eat more than you burn, you gain weight," says Abby Langer, a registered dietitian in Toronto, Ontario, and author of Good Food, Bad Diet. "And if you eat less, you lose [weight]."
But the CICO diet isn’t a magic bullet. That's because our various body types burn calories at a different rate. And this can make measuring calories complex.
Overall, it's best to make lasting lifestyle habits. And for some people, a simple diet plan like CICO can help. Learn more about CICO, how it works, and if it’s right for you.
What Is a CICO Diet?
"Calories in, calories out" means you eat less than you burn. “To encourage weight loss, the diet focuses on consuming fewer calories than what you expend,” says Kristen Smith, a spokesperson for the Academy of Nutrition and Dietetics.
To do this, track the calories you eat (calories in). And make sure you burn (calories out) more with exercise.
Is CICO the same as a calorie deficit?
CICO is the same thing as a "calorie deficit," says Langer. Most diets use less calories in, more calories out.
But many diets suggest certain protein, carbohydrate, or fat amounts. Or they cut out entire food groups. CICO simplifies all that.
How Does CICO Work?
To try the CICO diet, find out your basal metabolic rate (BMR). That's the least amount of calories your body burns at rest. It can vary, but on average the BMR is about:
1,700 for men
1,400 for women
You can use an online calculator like the one at Mayo Clinic or National Academy of Sports Medicine.
To figure out how many calories you consume each day, enter your:
Height
Weight
Age
Average activity level
With CICO, you focus on eating fewer calories than your BMR. So if your BMR is 1800, eat fewer to lose weight.
But the calculator isn't always correct. It can get your rate too high (overestimate) or too low (underestimate). That's because of different body shapes, muscle, and body fat amounts.
The calculator can get your BMR wrong if you:
Are pregnant or breastfeeding
Are a professional athlete
Have a metabolic problem like diabetes
What Can You Eat on a CICO Diet?
You can eat anything, as long as you eat fewer calories than you burn. “You can eat Twinkies all day long as long as you stay within a certain calorie limit,” says Langer.
But that’s not the best way to build healthy eating habits. “Four hundred calories of Twinkies don’t offer the same nutrients and health benefits as 400 calories of lean protein and fiber-rich foods like fruit,” says Langer.
If you follow the CICO diet, Langer suggests to get most calories from:
- Whole, unprocessed foods
- Fruits
- Vegetables
- Whole grains
- Nuts
- Lean protein like fish, seafood and poultry
Eating healthy is key for good overall well-being. Your food's macronutrients (carbs, fats, and protein) have a big impact on how full you feel. And healthier foods can help you stay full longer.
Does the CICO Diet Help Lose Weight?
Usually, fewer calories can help you lose weight. One study showed eating different amounts of protein, carbohydrates, and fat made no difference. But eating fewer calories did. And people lost similar weight, no matter which diet they followed.
The quality of your calories also counts, says Langer. Your body absorbs most calories from a muffin. But you only absorb about 20% of the calories from almonds. And a diet made up of ultra-processed foods can add roughly 500 more calories a day.
“Whole foods like fruits, vegetables, and whole grains are higher in fiber, which helps you feel full faster,” explains Langer. “You’ll naturally eat less because you won’t be as hungry.”
Is the CICO diet sustainable?
The CICO diet can help you reach your short-term weight loss goals. But it may be hard to keep up.
“It’s very hard to track calories so rigorously for an extended period of time,” says Langer. “A fixation on calories can also make you feel deprived, and you may get frustrated and give up.”
Benefits of the CICO Diet
Research shows most of us think we eat fewer calories in a day we really do. But if you track calories, you'll know more about your diet, says Langer. And this may help you lose weight.
The CICO diet is flexible, too. You can eat what you want — as long as you eat fewer calories. It works with a wide range of eating patterns.
You can follow the Mediterranean, DASH, or low-FODMAP diet. And with CICO, you can indulge sometimes. You can treat yourself to pizza or a brownie.
Studies show self-monitoring your daily food stats can also help.
Use paper or an app to log your:
Food and calorie intake
Physical activity
Weight
Recording these can help you successfully lose weight.
“It can also help you figure out where there’s room for improvement," says Langer. "For example, you may need to eat more fiber or more protein."
Potential Drawbacks of the CICO Diet
There's no one-size-fits-all method for weight loss. While the CICO diet may work for some, it won’t work for everyone.
Risks of nutritional deficiencies
The CICO diet allows any type of food. But eating mainly junk food means fewer nutrients. This can raise your risk for nutritional deficiency.
The most common vitamin deficiencies are:
Vitamin B6
Vitamin D
Iron
Weight loss plateau
It’s common to hit a weight loss plateau. At first, you may rapidly drop weight. That's because your body mostly burns calories in a type of stored glucose called glycogen.
But then you’ll start to lose muscle along with fat. This muscle loss can cause your metabolism to slow down. And burning fewer calories can slow your metabolism and weight loss.
“Our bodies fight back when we lose weight because they think we’re going into starvation mode,” says Langar.
Your body also releases ghrelin — the hunger hormone. And it's harder not to eat if you’re hungrier. You’ll need to drop even more calories or exercise more to lose weight, says Langar. But that may be hard to do.
Mental health issues
Some studies suggest higher risk for depression symptoms with calorie restricted diets. But people eating nutrient-based diets didn't report depression. And certain vitamin deficiencies can cause depression, too.
“It can also become very isolating to be on a strict CICO diet,” explains Langar. “You may avoid going out for dinner with friends, for example, because you worry you’ll blow through your calorie budget.”
It can become easy to feel guilty or ashamed if you go over your calorie limit. You may see this as a failure. And this can worsen how you feel about yourself.
Risk of worsening eating disorders
Using an app may make your eating disorder worse. A small study found that a group of 75 people with eating disorders used an app to track calories. And over 70 out of the group said the app made their symptoms worse.
“It may [worsen] a certain rigidity of thinking linked with an eating disorder,” says Langar.
Counting calories gets easier. But after doing it over and over all day, you may start to feel anxious about food. Especially if you don't know how many calories they have.
May not be suitable for everyone
Lifestyle choices (calories in and out) are just one factor affecting weight loss.
Weight loss can depend on your:
- Family genetics
- Medications
- Lifestyle choices (eating habits and exercise)
- Medical conditions
- Environment
- Sleep habits
One small study found personalized weight loss programs works best. “There’s no one cookie cutter approach to weight loss,” says Langer.
How to Try the CICO Diet Safely
The CICO diet is best with help from a registered dietitian nutritionist, says Smith. They can look at your eating habits and health. Your dietitian can also estimate your best calorie range. They'll also suggest nutritious and filling foods to eat.
Here are some safe ways to try the CICO diet.
Focus on whole foods
Eat low-calorie fruits, vegetables, and whole grains. These high-fiber foods help you feel full. They're also packed with nutrients.
Eat mindfully
Slow down and focus on each bite of food. You’ll enjoy the taste more and feel full faster.
Don’t go too low
Each day, you should eat at least 1,200 calories for women or 1,500 calories for men.
Try some simple swaps
Swap high-calorie foods for lower-calorie choices. Instead of a latte, try coffee with a little milk. For dessert, try a bowl of strawberries instead of ice cream. Craving savory? Have a cup of air popped popcorn instead of chips.
Takeaways
The CICO diet is simply “calories in, calories out.” You just eat fewer calories than your body burns each day. But the diet works short-term, raises your risk for nutritional deficiencies, and can trigger disordered eating patterns. To safely try CICO, talk to a registered dietitian nutritionist first.
FAQs About the CICO (Calories In, Calories Out) Diet
Will I lose weight if I burn all the calories I eat?
No, usually you’ll lose weight by burning more calories than you eat. A good rule of thumb is to burn about 500 more calories than you eat each day.
What is a realistic amount of weight to lose in 30 days?
“A 5% weight loss is a realistic goal for a 30-day time frame,” says Smith. For a 150-pound woman, that means about 7 1/2 pounds in a month.
Can you exercise on a CICO diet?
Yes, exercise is important for the CICO diet. Physical exercise helps you burn more calories than you eat. This can also help you lose weight. It builds muscle mass to keep up your metabolism.
Is a 1,200-calorie deficit diet good for weight loss?
A 1,200-calorie deficit isn't usually suggested for weight loss. Talk to your nutritionist, but a 500- to 750-calorie deficit is often suggested. And try to eat at least 1,200 calories a day for women or 1,500 a day for men.
