1. Since when lean individuals can't lose weight? Are they somehow immune to losing weight? Most of the other studies are done on obese individuals so I'm actually happy that they chose a different population.
2. The point of fasting for most people is to lose weight. You can think what you want but that's how it is. 99% of people don't give a damn about serum insulin levels. All they want to do is to use IF for weight loss (which is sad, of course) or purely because it fits their schedule. So again, I'm satisfied with the objective of this study.
3. "For weight loss research it is sub-optimal as compliance becomes a potential confound." That's why studies eliminate subjects if satisfactory compliance is not met.
4. "This study makes no mention of controls put on what, and more importantly for the fasting group, WHEN subjects in each group ate. So we don't know if the subjects in the "fasting group" really fasted." — get a subscription and read the full article. Just because you can only read the abstract doesn't mean that the study is flawed in that department. Or wait until it's published for the general population.
5. "Why were subjects in the fasting group told to overeat on fed days?" — because complete compensatory intake on the feeding days to offset the fasting days’ deficit does not occur. If they were to tell subjects to eat 100%, the results would be even worse in terms of health and fat-free markers. We've seen this countless times with VLCDs.
6. Insulin has nothing to do with fat loss inhibition so I'm surprised why you're so worried about it.
Say you wake up but you skip breakfast. Your body is now using stored fat for fuel. Later, you eat lunch—insulin surges, and your body stops burning stored energy and starts using calories you just consumed.
But that does not prevent fat loss from occurring because your body will quickly return to a natural state—glucose will be removed from the bloodstream and your metabolism will be humming along on a mix of fuels that includes more fat than glucose.
Consistently eat fewer calories than you burn and your body will spend more time burning stored fat than the energy you provide. Insulin is just doing its job - transporting nutrients because it's a regulatory hormone. It's not a fat-storage hormone as many people think.