What is CICO?
Published on August 2, 2025
CICO, short for Calories In, Calories Out, is a simple but powerful principle that explains how body weight is regulated. At its core, CICO refers to the balance between the calories you consume through food and drink (calories in) and the calories your body burns for energy (calories out). If you consume more than you burn, your body stores the excess as fat. If you burn more than you consume, you lose fat. This straightforward idea is the scientific foundation behind all successful weight loss strategies.
Why CICO Matters
Understanding the CICO principle empowers individuals to take control of their health and body composition. While many popular diets promise quick results through restrictive rules or trendy eating patterns, the underlying mechanism remains the same: a calorie deficit leads to fat loss. CICO provides a universal framework that applies to virtually all dietary approaches—from low-carb to high-carb, plant-based to carnivore. Recognizing this helps cut through nutritional noise and misinformation.
Your body requires a certain number of calories each day just to maintain basic functions such as breathing, circulation, and cellular repair—this is known as your Basal Metabolic Rate (BMR). Add to that your physical activity, digestion, and other daily movements, and you get your Total Daily Energy Expenditure (TDEE). When you consume fewer calories than your TDEE, your body draws on stored energy (primarily body fat) to make up the difference, resulting in weight loss.
How to Use CICO for Effective Weight Loss
- Determine your maintenance calories: Use an online TDEE calculator that considers your age, sex, weight, height, and activity level to estimate how many calories you need to maintain your weight.
- Set a realistic calorie deficit: A common recommendation is to reduce your intake by 10–25%. This creates sustainable fat loss without extreme hunger or fatigue.
- Track your intake and progress: Use a food-tracking app to log your meals and stay aware of your calorie consumption. Monitor your weight and how your clothes fit, and adjust as needed.
- Be consistent and patient: CICO works over time. Don’t expect overnight changes. Focus on long-term habits rather than quick fixes.
Importantly, weight fluctuations are normal and can be influenced by factors such as hydration, hormones, and food volume. Look for trends over time rather than daily numbers.
Debunking Common Myths
A frequent argument against CICO is the claim that “not all calories are equal.” While it's true that 100 calories of broccoli will affect your body differently than 100 calories of soda in terms of nutrition, satiety, and blood sugar response, the energy content remains the same. CICO isn’t about ignoring food quality—it simply states that regardless of what you eat, a calorie surplus will result in fat gain and a deficit will lead to fat loss.
Another myth is that CICO doesn’t work for people with slow metabolisms or hormonal issues. While individual differences exist, CICO still applies. These factors may influence your TDEE, but the basic principle remains valid.
Conclusion
CICO is not a diet—it’s a fundamental law of energy balance. Whether you prefer to eat six small meals a day or practice intermittent fasting, whether you're vegan or paleo, your success ultimately hinges on your calorie balance. Mastering the CICO principle gives you the freedom to choose a dietary approach that fits your preferences and lifestyle, while still making measurable progress toward your goals.
Infographic: Understanding Calories In vs. Calories Out