It's complicated. Reducing calorie intake is absolutely a path to weight loss, but we tend to ignore the adaptability of the body. If you suddenly reduce your caloric intake, the body thinks it's entering into a time of scarcity and will lower its metabolic rate through hormone modulation and by shedding muscle.
This is one reason why people struggle so much with dieting. They lose lot's of weight at first, but then plateau when the body adapts. When they get discouraged and fall off the diet, they put the weight back on quickly because they now are burning less calories than when they started.
The most effective way of losing weight long term is likely some combination of a slight caloric deficit paired with resistance training (to discourage the body from shedding metabolically expensive tissue) and short bouts of reverse dieting . (ie. slight deficit for 3 weeks, then 1 week of a slight surplus, etc.)
Calories not important. Type of calories important. Fibre contains calories, but they are locked up in a hard chemical shell that your body cannot crack, and therefore is unaffected by it. So, 200 calories of regular carbs are far more fattening than 200 calories of fibre carbs.
Edit: When I said that the body is unaffected by it, I was referring to the fact that fibre does no trigger the same cascading chemical reaction that other carbs do. No amount of fibre will cause an insulin spike and increased fat storage.
The types of foods (and NNSs) we consume, and the chemical affects they have, are more important than the amount we consume.
Yes, but it is not only the difference in available energy that is important. Fibre, although it is a sugar, does not trigger the same insulin response that other sugars (and NNSs) do.
This is largely incorrect, and also not what the person you're replying too is saying. Calorie numbers in food are just a weighted sum of the grams of carbs, fats, and proteins in the food. Each of those groups are assigned a fixed weight based on an estimate of how many usable calories are in a gram of each.
The commenter above is talking about how we often ignore the adaptability of the body, and that if you suddenly cut caloric intake by say 300 a day, the body will surprisingly quickly adapt by lowering metabolic rate to compensate. This can be done through the simple modulation of hormones and may also involve the shedding of metabolically expensive tissue, like muscle.
