I don't believe you need to reduce your calorie intake to lose weight
Nor do I. What've I said pretty consistently is that you need to modify your calorific intake to ensure you are running a deficit (once you take into account intake and expenditure [from both exercise and BMR]) in order to lose weight. There are many possibilities to this on a sliding scale:-
a) Do the same exercise and eat less than you were eating before
b) Eat the same as before but do more exercise
c) Eat more than before but do even more exercise
etc.
- you need to look at what calories you are taking on. A banana will give me on average around 150 calories, I could also get 150 calories from around 17 grams of butter. What would you have out of the two and why?
Choosing between a banana and butter for 150kcal is an entirely false dichotomy, whatever your calorific intake it should be a balance of fats, protein, carbs, etc all of the various different types in appropriate proportions.
You need a better understanding of insulin and what it does to the body, losing weight (and the onset of type II diabetes) is not about insulin spikes - it's about insulin sensitivity. Mashed potato on it's own, or mashed potato with a tuna steak, which do you think will lead to a higher level of insulin in the blood?
I'm sure we all need a better understanding, but following the videos of certain doctors have been useful. I'm not sure of the point of your specific question. Fasting is concerned with the longer term insulin response, not the specific response to individual meals.
And if you eat the appropriate foods (plant based) you won't need to calorie restrict to lose weight, you certainly won't need to starve yourself but not eating for x amount of days.
Again you misrepresent how most people approach fasting.
The concept of having to eat x calories per 24 hours is an entirely artificial construct. The human body does not fall apart if you don't eat for 24 hours or if you shift some of those calories around to previous/later days.
Instead, consider ensuring you eat 7x calories over 168 hours (7 days).
Lets assume someone is eating 2500kcal per day and maintaining their weight (so this is balanced with the exercise they do) and wants to lose 1lb a week. 1lb of fat is roughly 3500 kcal so that's the target deficit per week.
Current: 2500 * 7 = 17500 kcal/week
New Target: 17500 - 3500 = 14000 kcal/week
They can either target 14000/7 = 2000 kcal/day or opt for a 5:2 fasting model such as:-
(14000-1000)/5 = 2600 kcal/day for 5 days, plus two days at 500 kcal. (Which is a typical 5:2 style.) That still adds up to 14000kcal per week, so sustain this and if the average expenditure really is 2500kcal per day then it will lead to weight loss (if they keep up the exercise they were doing before, etc).
None of this emotive 'starving yourself' stuff, just two days of really cutting back that, as you'll find here, the people who do this have no problem with.