If you are overweight, your body has excess fat stores for energy. The point of IF is to reduce your fat stores by giving a window for your body to consume them. Which is what we want. The more time the body spends drawing energy from fat stores the more fat we loose. So why do people talk about “needing to eat enough calories” in their meals when fasting for weight loss on something like OMAD? Isnt eating beyond feeling full for the sake of getting more calories a little superfluous and slowing down weight loss? If it’s about nutrition wouldnt it be better to think, I should make sure my meal is nutritious and satiating rather than eating extra calories just because?
A) you’re right that you need to get enough nutrition to see you through your fasting period (rather than just calories). You need to get enough sodium, potassium, vitamin B, etc during your meal so that you don’t get a deficiency. Otherwise over a few prolonged fasts you may start to show some uncomfortable symptoms.
B) you should lose weight at a healthy rate - (I believe) losing too much in one go can be stressful on your heart/organs. So you need to calculate your maintenance calories (eg 1700), then figure out your appropriate calorie deficit to lose weight (eg 500), and then make sure you eat the proper amount of calories to strike the balance (~1200). There are calorie calculators online to find healthy amounts for your height/weight etc. It’s not like ‘more is better’ or just because, it’s about striking the balance.
C) if you continuously eat too few calories you will enter starvation mode and your metabolic rate will slow, your weight loss progress will struggle. You need to occassionally tell your body that you’re not starving, you’re getting the energy & nutrients you need, but between meals you’re relying on those fat reserves.