Key idea: Muscles are well equipped to oxidize fat, as opposed to other tissues, which absolutely need sugar to function.
Losing weight is not a mindless process of restricting calories. The hip approach for several decades already has been to ”burn fat”, but I don’t think there’s anything safe about that process of ketosis (restricting carbohydrates to shift to fat burning). (1)
Fasting is even worse, as Ray Peat put it so simply in a recent podcast, for most people, a fast is basically a ”100% pure PUFA diet”, simply because of our modern world, and the rampant use of these vegetable and seed oils in everything, our fat tissues are filled with these easily oxidized unsaturated fats and those become the fuel source whenever blood sugar drops. It’s a frightening thought when we think of how carbs and sugar have been demonized over the decades. Low sugar, high PUFA is one hell of a combo.
In a low-blood sugar state, cortisol proceeds to break down connective tissues for energy, and if your face has started sagging in the past few years, that’s a tell tale sign, as is accumulation of fat around the midsection, the classic high cortisol shape. Truly, one could say that from an evolutionary perspective, a low-blood sugar state is a state of stress, and an indicator of scarcity of resources, which prompts the accumulation of fat as a precautionary measure.
Simply put, a safe way to reduce weight is to get healthier, eat lots of easy-to-digest carbohydrates (fruits, simple sugar, honey, well cooked potatoes, white rice, etc.) raise your thyroid function and by extension rate of metabolism, eat saturated fats and slowly build muscles with easy exercise, while aiming to lose 1-2 pounds a week at the most. With a high rate of metabolism, your muscles will safely burn the excess fat at rest, while you keep on providing abundant energy (carbs) for your other tissues (i.e. brain).
(1) Mamounis, Kyle. Why you don’t want to be a fat burner (2017) https://jevohealth.com/journal/vol2/iss1/9/