An article at gnolls.org claims that there is no such thing as a calorie to our body, and our stomachs aren't steam engines and therefore the concept of calories and our way of measuring them is unhelpful.
The concept of the “calorie”, as applied to nutrition, is an oversimplification so extreme as to be untrue in practice.
Another article at The Healthy Omnivore claims that CICO (calories in, calories out) is a myth, because of biochemical individuality. Quoting the article:
- Genetics: What is your ancestry? Are you from a cold climate or warm climate? How does your body handle starchy carbohydrates? How does your body handle fatty proteins? How do you do with the sun? Etc. Etc. Etc. Secondly, physiologically, how have we handled our environment and time.
- Sleep (Are you allowing your body to recover?)
- Toxins (Tobacco, Alcohol, Sugar, Artificial Sweeteners)
- Food Sensitivities (Gluten, Soy, Dairy, etc.)
- Medications (Over The Counter, Prescription)
- Stress (Chronic and Acute)
- Quality of Health (Recent Illnesses, Immune System Health, Degenerative Disease, etc.)
- Hormonal Health (Insulin, Cortisol, Glucagon, Leptin, etc.)
- Age (Menopause, Andropause, Accelerated Aging)
- Past Caloric Restriction History (Dieting, Bulimia, Anorexia, etc.)
Common sense would tell me that all the above factors do play a role, but that this role has limits.