The body basically has a bunch of tricks for tricking you into not losing weight. It starts making you subtly lazier, reduces random energy expenditures, slows down basal metabolic rate, it makes you hungrier, it makes you crave more calorie dense food, and it even starts to reduce willpower related to food.
Absolutely this. Our body is constantly trying to maintain homeostasis, so when you make a big lifestyle change your body tries to react in the opposite direction.
Most people don't understand that when you start a new habit it often replaces another. When you start going to the gym you might walk less. When you eat smaller meals you might snack more. etc. I'd love to see a list of all the unconscious decisions your body makes in response to fitness/nutrition interventions.
