Several factors affecting body weight. Highlighting each person is so unique. What works for one, doesn't for another. Also, nutritional health is not calories in, calories out. This is too reductionist and not useful.
Some of these factors affecting body weight.
Nutrition
Stress
Breath
Thyroid function
Genetics
Blood Sugar & insulin sensitivity
Movement
Appetite
Neuropeptides
Food Sensitivities
Alcohol
Prescription Meds
Hormones
Liver & toxins
Eating disorders
Gut health
Varying dis-eases