I’m still a little confused about where and how fasting and CICO overlap. Extremely popular (and apparently effective, too) apps such as Noom live and die by CICO, but fasting techniques such as IF seem to preach that CICO doesn’t really matter - what matters is when you eat your food and going at least 16 consecutive hours without eating so that your metabolism speeds up and you burn fast faster due to lower blood insulin levels. So – which is right? Or are they both right? I know fasting is effective because I’ve experienced the benefits of it over the last 6 months without tracking calories or caring about CICO. But I’m also wondering if my fasting would be even more effective with CICO. Perhaps the best way to phrase this question is: If in the 3-hour mid-dat eating window I’ve been doing for fasting I ate the same amount or more calories than I would eat in a regular 3-meal day, would I still gain weight?
u/Ford88, CICO as a weight loss strategy is just plain unhelpful and too simplistic. Suppose you’re consuming 3000 calories a day and burning 3000 calories a day. But you’re thirty pounds overweight. You decide to go into caloric deficit to lose the thirty pounds. You carefully consume only 2500 calories per day. You start to lose a few pounds, maybe.
But the surly “It’s all CICO you science deniers” people do not take into account that something else may happen. Your metabolism may drop to 2500. At this point, you’re consuming 2500 cal/day and burning 2500 cal/day, and now you’re no longer losing weight. This phenomenon is fairly well documented in a number of studies. I’m pretty sure it’s happened to me. I’m sure many others will claim it’s happened to them. Arguably, it’s one of the main reasons so many fail at “dieting” by simply going into caloric deficit. Hence the claim that CICO is unhelpful as a weight loss strategy.
The trick is to create a caloric deficit at 2500 cal/day while maintaining your total metabolism at 3000 or thereabouts so that you will consistently lose weight. How do you do that? Fasting, it is argued by many scientists and doctors, does this, because when you fast, your blood glucose level drops. Then, your insulin drops. When insulin drops, counter-regulatory hormones like cortisol, glucagon, epinephrine, etc., rise. These hormones free up fatty acids for utilization as energy. Ideally, you burn the 500 calories in fat that you need to keep your total metabolism at 3000 calories per day. Hence, your metabolism does not drop and you keep burning fat and losing weight.
The cases in which you go into caloric deficit but your metabolism drops and you stop losing weight are associated with carb rich diets. Even though you are in caloric deficit, the carbohydrates keep your blood sugar levels up, and hence your insulin levels up. Then, with insulin up, your counter-regulatory hormones are suppressed, and the utilization of fat as an energy source is blocked. If there’s no other source of energy, your body will start to recognize that it’s not getting any more than 2500 calories per day. It adjusts accordingly and drops your metabolism to 2500. You may experience this as lethargy and coldness.
This is largely just Dr. Jason Fung’s explanation. He has a YouTube channel under his name with a number of videos discussing this, including some of the science that backs it up. It’s certainly not scientific orthodoxy. From what I can tell, there is no consensus here. There is though a significant group of scientists and doctors who advance this or a similar view of the relationship between weight loss, hormones, and fasting (or other means for controlling hormones). It’s sometimes called the “carbohydrate-insulin” model.
All fasting is is a way to control CICO. That’s literally the only way to lose weight. To expend more energy than you’re intaking. Anything else is just a different way to sell that.
Does fasting work? Absolutely. Is it because you’re expending more calories than you’re intaking? Absolutely
People who rely on CICO are going to be disappointed in the long term. CICO doesn’t consider food quality and macronutrient intake. People act like they’re calculators and ignore the complex organism they truly are.
Can you lose weight for a while? Sure. But are you so sure you’re only cannibalizing fat for energy? What are you doing to your hormones? What are you doing to your metabolism?
Here’s an example. I’m a 35 y/o male. Starting weight was 205 3ish months ago. If you put my weight into any TDEE calculator, it will tell you my maintenance calories are somewhere near 1950 calories.
Trouble with that is, that’s wrong. I’m sedentary. I don’t work out. So what I’m about to say will probably not make sense to someone in the CICO school of thought.
I have been strict carnivore for the last 3 months, eating any where between 2-4 pounds of beef daily. Google will tell you that this caloric intake would be estimated around 3012-6024 calories (70/30 ground beef). So if my TDEE is 1950, that means on average I ate nearly 2600 calories more than my maintenance ought to be for 92 days.
So, I should have gained 67.50 pounds.
So why did I lose 10 pounds instead?
Maybe because CICO isn’t all it’s cracked up to be.