Many people claim that CICO (Calories In, Calories Out) is the ultimate rule for weight loss, emphasizing that a caloric deficit should lead to shedding pounds. For young, healthy individuals, this principle generally holds true. However, weight management isn’t always as straightforward as balancing energy intake and expenditure. Various physiological, hormonal, and lifestyle factors can complicate the process, influencing how the body responds to calorie deficits and impacting weight loss outcomes.

If you’re consuming fewer calories than your Total Daily Energy Expenditure (TDEE) but not losing weight, several factors might be influencing this outcome:

1. Inaccurate Calorie Tracking: One of the most common reasons is underestimating calorie intake. This can happen if portion sizes are not measured accurately, or if certain high-calorie foods or snacks are overlooked.
2. Hidden Calories: Calories from condiments, dressings, oils, and beverages can add up and may be missed in daily tracking.
3. Metabolic Adaptation: Over time, the body can adapt to a lower calorie intake by slowing down metabolism. This is sometimes called “adaptive thermogenesis” and can make weight loss more difficult.
4. Inconsistent Caloric Deficit: Occasional overeating or “cheat days” can offset the caloric deficit and lead to weight maintenance rather than loss.
5. Hormonal Imbalances: Conditions like hypothyroidism, polycystic ovary syndrome (PCOS), or elevated cortisol levels due to stress can affect metabolism and hinder weight loss. ^source
6. Water Retention: Factors such as increased sodium intake, hormonal fluctuations, or inflammation can cause the body to retain water, masking fat loss.
7. Lack of Sleep: Poor sleep can impact hunger hormones (ghrelin and leptin) and lead to increased hunger and reduced energy expenditure.
8. Muscle Gain: If someone is doing resistance training or engaging in physical activities, they might be gaining muscle while losing fat, which can result in a stable or even increased weight.
9. Medical Conditions or Medications: Certain medications (e.g., antidepressants, antipsychotics, and some birth control pills) and health conditions can contribute to weight retention.
10. Gut Health and Digestion: Poor gut health can affect how the body absorbs nutrients and processes food, which may impact weight.

Identifying the specific cause may require closer analysis of food intake, lifestyle factors, and potentially seeking guidance from a healthcare professional for comprehensive evaluation and support.

While CICO remains a foundational concept in weight management, it’s crucial to recognize that it may not be the sole factor at play, especially for individuals facing unique metabolic or health challenges. Factors such as hormonal imbalances, metabolic adaptation, and medication use can all affect the body’s response to caloric intake. For those struggling to lose weight despite adhering to CICO principles, understanding these potential barriers and seeking professional guidance can be essential for achieving sustainable results.