What Is the CICO Diet, and Can It Help You Manage Weight?

Is it possible to have your cake and eat it, too, as long as you burn enough calories to make up for it? In a way, that’s the idea behind the “calories in, calories out” (CICO) diet, a twist on a time-tested principle of weight loss: As long as you burn more calories than you ingest, you will lose weight.

But some people are taking that as a license to live on junk food — as long as the math works out. Check out the #CICO hashtag on Instagram and you will see images of Pop-Tarts, pie, potato chips, pizza, and poutine offered up as evidence that you can indulge and still shed pounds. Meanwhile, Reddit users have posted thousands of messages about the diet.

Convenience and quick results, say proponents, are two major reasons for using the approach. But does the diet help you lose weight safely and actually keep it off? That’s where the science gets far murkier.

How Does the CICO Diet Work?

“The foundation of weight loss is purely related to the relationship between the number of calories you take in and the number of calories you burn,” explains Paul Salter, RD, CSCS, a nutritionist and sustainable weight loss expert practicing in Valrico, Florida. “If you’re in a deficit, you’re going to lose weight. Conversely, if you’re in a surplus, you’re going to gain weight.”

“Many people who have started to do a little more math and track their food realize that, ‘Yes, I can essentially get away with eating anything I want as long as I’m eating fewer calories than I burn,’” says Salter, explaining that the researcher who popularized the CICO concept primarily ate Hostess snacks, such as Twinkies and Ho-Hos, yet dropped weight.

At the end of 10 weeks, Dr. Haub had lost 27 pounds (lb), for a final weight of 174 lb. His body mass index (BMI) dropped from 28.8, which is considered overweight, to 24.9, which is deemed normal. His cholesterol readings improved, too, likely a result of his weight loss.

And that’s the appeal of the CICO diet: Technically, you can eat anything on the CICO diet, as long as you burn more calories than you take in.

Benefits and Risks of the CICO Diet

However, practitioners of the current CICO diet focus on calorie reduction without regard to the balance of nutrients they take in, and they find that it works. That said, malnutrition is a real risk with the CICO diet if it revolves around junk food or nutrient-poor choices. “If we’re eating nothing but Twinkies all day, we’re missing essential vitamins, minerals, antioxidants, phytonutrients, fiber — probably lacking protein, probably lacking healthy fat,” says Salter.

“That is not ideal for our overall functioning, both cognitively and physically. If we go one step further, a lot of people misunderstand the fact that each nutrient — carbohydrates, protein, and fat — behaves differently in the body.”

He provides the example of complex carbohydrates, such as brown rice, quinoa, and whole-grain products, which are notoriously missing from a junk-food diet. “What makes them so beneficial is not only the vitamin and mineral content, but the fact that they have fiber, which slows down digestion, keeps energy levels steady, and appetite under control for the next few hours after a meal.”

A closer look at Haub’s experiment reveals an attempt at nutritional balance. While two-thirds of his diet was junk food, he also took a daily multivitamin pill and drank a protein shake. Plus, he typically ate a can of green beans or three to four celery stalks on top of the snack food. The nutrients those additions provided may have affected his results.

Junk food aside, obsessing over calorie counting has a downside, says Amanda Goodwin, RDN, a registered dietician. Don’t get so giddy about eating sweet treats every day while you lose weight that you neglect to take in enough calories. That can backfire in the long run.

“You have to make sure you’re getting enough calories at each meal and in between meals to sustain your metabolism and also your energy level so that you’re not ready to binge by the time the office snacks come around at 3 p.m. or by the time you’re resting on the couch after dinner,” Goodwin cautions.

In fact, Goodwin doesn’t give her clients calorie restrictions at all. She says that she has seen too many diets derailed because a fixation on calories left a client feeling deprived, making their regimen unsustainable.

Can the CICO Diet Help You Lose Weight?

In the short term, you are likely to lose weight by strictly adhering to the “calories in, calories out” approach, regardless of what you eat. But experts caution that, in the long run, it can be difficult and unhealthy to sustain. Focus instead on eating a well-balanced diet and regularly engaging in some form of exercise you enjoy, advises Salter.

The Takeaway

• The “calories in, calories out” (CICO) diet is a weight loss approach that says if you eat fewer calories and burn more calories, you’ll lose weight.
• Research says that this concept isn’t so simple because everyone’s weight can fluctuate based on factors like metabolism, hormones, and overall health status.
• While this diet plan can help support weight loss initially, it may be difficult to sustain over time.