That workout frequency is an interesting take. Do you have any articles on it or only anecdotal evidence?
This is a great question. I've read things alluding to this in many places, I believe including Lyle McDonald's work. Obviously, I like to think I'm indestructible, so I learned it somewhere but don't always listen. But, as I've experimented on myself, this experience has shown me that - the more exercise I do, the harder it becomes to stick to a strict diet. Keep in mind when I say strict, I mean extreme as I did a lot of PSMF dieting over the past 2 years.
So your question is a great one and I just did a quick search for my own curiosity and these came up pretty quickly:
This study:
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Suggests that exercise doesn't acutely reduce leptin levels unless it is long bouts greater than 60 minutes. As I'm reading the study, I am feeling my own experience rings true - I was doing 1-2 hour bouts of cardio when things got really bad - but they didn't get bad gradually. I was doing it for weeks and then suddenly it was like a switch where I became ravenous and lost control. I'm not saying I was binging - but I WAS searching out sugary foods such as donuts, pastries, etc. - things I hadn't looked for in a while and I was craving them badly enough that I felt resisting the urge was actually unhealthy. In other words - I think chronic, long bouts of exercise will cause issues that build until it just hits all at once. This study seems to "point" in that direction, although it isn't exactly definitive.
Here's another study, more simplistic, that shows fasting and then exercising will reduce leptin levels. Again, it's an extreme situation, but points in the direction:
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I scanned this study and found it interesting that after a 12-week aerobic program, it showed that women had leptin drops but men did not. Interestingly, there wasn't a decrease in fat mass - which means the leptin drop wasn't caused by reduced fat - the exercise itself played some kind of role.
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This study shows, at least in the abstract (didn't read it all) that even short term exercise can impact leptin levels:
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And a study in children that shows leptin decreases during 4 month periods of training vs. 4 month periods of non-training:
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Everyone always talks about "starvation mode" and "metabolic damage" as if your metabolism is being damaged and you are burning fewer calories. I think this is somewhat naïve and over played. The REAL issue is perception and things that happen in the background that actually control our actions and we don't even realize. It isn't about will power. It's about the fact that starving yourself changes hormones that, once you get to a certain point, these hormones will make it near impossible for your to resist the call. Which is what you would expect. How long can you go without peeing? Sure, you can hold it. But after a while, your body will signal your brain that it needs to happen and you won't be able to resist, and most likely won't have any desire - even if it means pissing your pants.
Exercise, I believe, has a huge impact on this. People diet (regardless if it's 250 calories/day or 1,500 calories/day less than they normally eat) and exercise, and if they are creating too much stress through exercise in ANY deficit, their body will search for the materials to repair itself. This means that when they come off a diet, they are primed to over eat even if they don't realize it.
This is why I say pre-planned refeeds may be better than waiting for your body to tell you something is wrong.
Lol -sorry for the rant, but it was an interesting question and it got me thinking!