Based on my personal experience, I think it depends. Some of us were very fat. Once someone gets obese, their insulin control often goes out of whack. You can then restrict calories and have your body turn to muscle tissue for more calories while leaving the fat...not untouched, but certainly not used exclusively to make up the difference. For people like me, it really IS about insulin.
My sister was never fat. She didn’t LIKE cookies growing up so, unlike me, she didn’t grow up eating a dozen or more cookies a day! For her, reducing calories IS the answer. Her body never got out of whack in how it works. Mine did.
Another friend is the same way. Never got fat. What diet he uses doesn’t matter. If he starts to gain, he cuts back a little until the fat is gone. His body, like my sister’s, works the way it ought.
Mine? If all I cut is calories, I get weak as a kitten. If I aggressively cut carbs, the weight goes away without hunger or weakness.
For 80% of the population, what I say is true in terms that keeping your carbs in check and checking your bodyfat to keep it in line for you gender will generally keep diabetes away.
However, there is always genetics. For example, it is thought that diabetes is a consequences of being cold weather adapted. That’s why American natives and Germans tend to have higher rates than other populations. They are efficient users of carbohydrate calories, which helps get the sugar in the blood because blood sugar acts like antifreeze for the blood.
I think for most people, controlling the intake of short carbohydrate chains, which are basically processed sugars, and keeping the fat within their gender norms will almost never get diabetes. Although, what I say is true for the broad population, there may be some people who need more than that preventative step to ensure they don’t get diabetes.
I’m sure you a nice guy, but all that is anec-data. One or two person mini-pockets of incomplete data. There are going to be exceptions to any general rule, and I would also submit that even with these one or two person stories, the data is incomplete.
My recommendation is to start by watching the YouTube videos and listening to the podcasts of people like Andrew Huberman, Thomas DeLauro, Andy Galpin, Dr Berg, Peter Attia, David Sinclair, and the like. They are pretty consistent with their recommendations across the board: no sugar, limited carbs, no processed foods, push the exercise, sleep well, reduce stress. Nothing wacky or too strenuous. Treat your body as it was designed by The Designer.
1 Corinthians 6:19-20
New International Version
Do you not know that your bodies are temples of the Holy Spirit, who is in you, whom you have received from God? You are not your own; you were bought at a price. Therefore honor God with your bodies.