Whether you’re aiming to lose or gain weight, practicing the CICO diet—which stands for calories in calories out—offers one way to help you maintain a balance between taking in energy and expending it.
Nutrition is a huge part of training. You have to pay attention to what you eat to ensure you’re getting the right nutrients. And you might also want to know how much to eat to guarantee you have enough fuel to sustain your workouts, repair muscle, and keep up with day-to-day activities.
We spoke with two registered dieticians to find out the details about the CICO diet and how it might help your training—and what you need to know to follow it safely.
What is the CICO diet?
The term CICO is an acronym that stands for “calories in, calories out,” and it’s an old-school style of eating that has been widely used to help people achieve weight loss—but it can be much more than that.
“[CICO is] basically just the law of energy balance, meaning, if you want to maintain your weight, your calories in should equal your calories out,” Namrita Brooke, Ph.D., R.D.N. sports dietitian and cycling coach at Velocious in Pensacola, Florida tells Bicycling. Practicing this diet can be beneficial if you’re interested in losing, maintaining, or gaining weight Brooke says, but as with most diets, it has its limitations.
To successfully follow a CICO diet, you must truly understand your daily energy needs. That starts with defining your metabolic rate, which helps you identify the amount of energy your body needs to maintain daily activities, says Brooke. You’ll also need more calories to support all your rides, so that plays a role in figuring out your energy needs.
You can calculate your metabolic rate by using one of the basal metabolic rate equations, testing at a local lab, or working with a registered dietitian.
Then, depending on your goal, you can use this number to calculate the number of calories you need each day. Keep in mind, any number you calculate is only an estimate of what your body actually needs.
The CICO Formula:
- To maintain energy balance: calories in = calories out
- For a calorie deficit: calories in < calories out
- For a calorie surplus: calories in > calories out
The CICO diet is known for focusing on how much you eat rather than what you eat. But that doesn’t mean you don’t need to make nutritious choices, especially if you want to enhance performance. For example, Brooke says, even though a burger might have the same number of calories as a salad and a smoothie combined, it won’t provide the same level of nutrients, and that is still an important factor when it comes to energy needs, as well as overall health and how well you perform on your rides.
What are the benefits of the CICO diet?
Practicing this diet can be a learning opportunity. For example, you might learn more about the nutritional value of the foods you eat by monitoring your meals and snacks using a nutrition tracker like, MyFitnessPal. Brooke says tracking what you eat can help you spot the nutrition gaps in your diet, especially if you’re jotting down your foods. That’s why this style of eating can serve more people than just those seeking to lose weight.
For those looking to lose weight, the CICO diet can also help you maintain a healthy calorie deficit, which means the number of calories taken in is less than the number of calories you burn.
Alex Larson, M.S., R.D.N., L.D., and triathlete who specialises in endurance performance nutrition says that to find a healthy calorie deficit, consider calculating it as a percentage. She suggests aiming for a 15-percent calorie deficit for slow, healthy weight loss. This will still give you enough energy to hit your cycling goals. For example, she says, if someone would normally eat about 2,200 calories a day, then a healthy calorie deficit would involve cutting that total number by 330 calories.
For lose aiming to gain weight or build muscle, you can use the CICO diet as well. “Tracking your calories to put yourself at a slight calorie surplus combined with some strength training can be a very effective tactic to increasing muscle mass,” Larson says.
What are the downsides to the CICO diet?
When it comes to weight loss or maintenance, the biggest danger with the CICO diet is even if you’re calories in equals your calories out—meaning you’re maintaining an energy balance—you can still have low energy availability, says Brooke. This is why it’s important to factor in day-to-day activities.
“After you’re done with a bike ride, your body is burning a lot of energy to recover from that ride to build muscle, to build enzymes and hormones, and restore carbohydrate in your muscle,” Brooke says. So, you need to make sure you’re getting adequate calories to make sure your body can carry out these processes. The issue with a CICO diet, particularly if you’re looking to take in fewer calories than you burn, is that you might not be getting enough energy to support your workouts, as well as your needs for daily function. That’s why it’s beneficial to work with a dietitian, as well as pay close attention to how you’re feeling and what your energy levels are like.
“Sometimes people can take it too far and they can go toward too much of a calorie deficit. And that can be very harmful because their body isn’t getting enough energy,” Larson says. This can lead to chronic fatigue while cycling, headaches, trouble sleeping, missed menstrual periods, and even injury in some cases.
Another factor to consider before you try the CICO diet, Larson says, is your body will naturally adapt to maintain an energy balance. “When it comes to weight loss, most people will see some sort of plateau in that weight loss where they’re not losing any more pounds, but they’re still eating at a calorie deficit,” she says. Depending on your goal, this plateau may require you to eat even less to maintain some sort of deficit, which isn’t always sustainable (or enjoyable) in the long-term, she says.
What’s more, with so much of a focus on calorie counting with the CICO diet, following it can increase your risk of disordered eating habits. “It can lead people down the road of always trying to eat less, or only choosing foods because of their low-calorie level and not necessarily choosing foods because of their nutrient level,” Larson says. With that in mind, eating nutrient-dense foods—not to mention eating foods that you enjoy—is super important to your daily life, as well as your cycling training.
The Bottom Line on the CICO Diet
Regardless of your end goal, it’s helpful to learn your energy needs to support your training and day-to-day activities. But it’s also important to eat a nutrient-rich diet that you enjoy and can sustain. The CICO diet can be used periodically to help you achieve your nutrition goals, but if you notice disordered eating habits or it’s just taking the joy out of eating, skip it. There’s more to food and exercise than calories in versus calories out, so keep that in mind when considering this diet.