First, a music video. What else but...?
Part 1. Get slimmer.
Insulin increases the amount of nutrients entering adipocytes, which makes us fat and hungry.
Er, just a minute!
If increasing the amount of nutrients entering cells makes us hungry, exercise (which increases the amount of nutrients entering muscle cells) would make us hungry. It doesn't. See Fig. 1. in Influence of resistance and aerobic exercise on hunger, circulating levels of acylated ghrelin, and peptide YY in healthy males.
If going for a walk outdoors makes you hungry, you're doing it wrong. Wrap up warm, as feeling cold increases hunger. Low blood glucose level also increases hunger, so don't over-exercise while on a long-term ketogenic diet.
By the way, insulin also increases the amount of nutrients entering muscle cells.
Q. What determines the relative amounts of nutrients entering adipocytes vs muscle cells?
A. The relative insulin sensitivities of adipocytes vs muscle cells.
Adipocytes are sensitive to insulin until they become full. To reduce the amount of nutrients entering adipocytes, divert more nutrients to muscle cells by increasing their insulin sensitivity. Emptying muscle cells by doing low-intensity exercise increases their insulin sensitivity. High-intensity exercise increases their insulin sensitivity.
Part 2. Prevent/reverse age-related sarcopenia (muscle loss).
See Use 'em or lose 'em. As diverting more nutrients to muscle cells increases muscle mass, increasing their insulin sensitivity results in increased muscle mass, unless you're eating way below maintenance calories. High-intensity exercise results in more muscle mass gain than low-intensity exercise.
Part 3. Make your brain work properly.
Thanks to Chris Highcock, who gave me a complimentary copy of Hillfit, I found IL-6 and IL-10 Anti-Inflammatory Activity Links Exercise to Hypothalamic Insulin and Leptin Sensitivity through IKKβ and ER Stress Inhibition.
In plain English, this means that exercise increases both insulin and leptin sensitivity in the hypothalamus. As the hypothalamus controls appetite and both insulin & leptin are appetite-suppressing, the net result is less appetite.