I often read that when weight is lost that we also lose muscle and therefore get a dip in BMR which causes weight gain further down the line. Given this, does weight loss via IF last, or do most people regain?
The short answer is yes, weight loss with IF is sustainable, as long as you keep your insulin low enough. :)
That drop in BMR you mentioned actually corresponds with calorie restriction diets that still have high insulin levels. Insulin is what directs the body on how to use the incoming food energy. If insulin is high (which happens if you eat frequent meals/snacks, or high carbs, or have insulin resistance), your body directs that food toward fat storage rather than burning it as energy. Combine that with calorie restriction, and your BMR goes down, hunger goes up, and weight comes back in about 6 months.
IF is different because it lowers insulin. So, food comes in and gets burned rather than stored. Your low insulin also allows energy to be used from your fat stores, which keeps your BMR high and keeps the weight off. Great news all around!
Here’s a talk by Dr. Jason Fung where he goes into the studies behind this concept: https://youtu.be/ZKC3hiyLeRc
My simplistic view is that, regardless of dietary protocol, most of those who regain do so 90% because of old habits (less movement and/or greater consumption) creeping back in and only 10% because of metabolic slow-down. Metabolic adaptation is an inevitable artifact of weight loss, even if 100% of one’s original muscle mass is maintained (or even increased). For one, fat mass is metabolically active too. For two, and most importantly, it is NEAT that is virtually guaranteed to decline past weight loss, not so much BMR, for the simple reason that “fighting gravity” every minute of the day just isn’t as energetically taxing for a light individual compared to their heavier former self. But again, a 100~500kcal/day reduction in energy expenditure won’t stop someone from maintaining, if that’s their heart’s desire; it’s the 3 binge nights a week of 5k kcal each, brought on by life stressors and lack of non-food sources of joy, that most certainly will.
Personally I favor simplicity. Once I’m done losing (should be any day now) and so long as I’m functioning satisfactorily, my intent is to just keep on practicing OMAD indefinitely. I may allow myself a third serving or a glass of alcohol when feeling like it, but that’s about as far as I’m willing to loosen up on a daily basis; if I revert to free grazing and sipping down liter after liter of sweetened beverage day in and out from dawn till dusk, I know for a fact I’ll be right back where I started in no time.
Definitely, because IF makes you more disciplined in terms of appetite, that’s also how you crave for unhealthy food less, thus lose those unhealthy weights steadily. At least for me, this is what IF has done to me. No longer yo-yo effect, weight bounce back, bad cravings (except during PMS), etc.
Plus, you can always regain muscle mass by incorporating weight lifting, which is essential for bone health and joint protection as we age, if we are thinking long run, then it is almost logical to not depend on IF alone, I say this w the utmost respect!