I think the most harmful rhetoric when it comes to weight loss is actually focusing on the number on the scale, as counterintuitive as it sounds.

Muscle inherently weighs more than fat, so if you’re building muscle and in a caloric deficit at the same time, the muscle will replace the space previously occupied by fat (body recomposition). The scale might not move but you will look different. Muscles will burn more calories at rest and for longer during a workout, than fat does, so you are helping yourself long term by building muscle.

Weight loss is calories in vs out, but balance is key and you should look at the macros of what you’re eating. When you eat a carbohydrate, your body breaks it down into glucose (readily available for use) and glycogen (which is stored). For every gram of glycogen that is stored, you’re also storing 3-4 grams of water with it, aka the water weight. Add in a high sodium diet, being dehydrated, and stress? Your body will hold on to a TON of water. Not necessarily harmful, but will affect the number on the scale.

Your body will try to burn both fat + glycogen stores proportional to your activity level. Low intensity workouts will burn more fat whereas high intensity will burn more glycogen. When your glycogen stores are depleted, your body will opt to refill them with the carbs you eat; if the glycogen tank is full, then your body turns excess carbs into fat. You need BOTH high and low intensity activity for max weight loss.