I know everyone would like a simple rule and be done with it, but the human body is more complex than that. Calories do matter but there are three fundamental flaws with the calories in/calories out model: 1) calories in is an estimate; 2: Calories out is an estimate; and 3) hormones have a huge effect on your daily calorie needs. So, rule #1, don’t stress so much on the calorie stuff. In fact, the stress makes it even harder to lose fat.
There is some science to support the fact that you can lower your metabolism if you starve yourself (https://en.wikipedia.org/wiki/Minnesota_Starvation_Experiment), but that was under and extreme condition. So what if you feel comfortable eating 1000 calories and your metabolism drops a bit? There is also science to support that a lower metabolism is good for increased longevity. And you’re likely right that your body is getting calories from fat, balancing the formula.
If I were to break it down to one rule, it would be this: How do you look and feel? How is your energy level? Are you able to do the things you want to do without fatiguing too soon?
You’ll need to eat to get the nutrition your body needs (micronutrients) and the fats and protein necessary to fuel and rebuild your body. So with that in mind, eat what and when you want to eat.
I’ve had this same conundrum after dropping my eating window to OMAD. Last night I was so uncomfortably full, and I even ate a good chunk of higher carb/less satiating foods. I am never eating enough in that window, but I am energetic and feeling great, so I will carry on.
(She had one feck to give and that feck is gone.)
I agree. Listen to your body’s signals as long as you feel great, are making improvements in your health goals and you are getting your life stuff done.
Thank you for asking this - I’ve had the same question on my mind. When I’ve tried OMAD it’s been a challenge to eat “enough” calories if I only eat to satiety, so I feel conflicted because of the parallel advice that restricting calories can lower your metabolism and in the long run make it harder to keep the weight off. The advice of “don’t worry about calories” isn’t helpful in this instance as it’s too vague and doesn’t answer the question. #SoConfused
@richard can you clarify? Should we concern ourselves with lowering our metabolism if “to satiety” = too calorie restricted? I’ve seen you answer this elsewhere saying “if you’re fat adapted, feeling good, etc you’re ok” but I don’t feel like we really got to the heart of the matter regarding the long term impact on our weight set point and metabolism. Are we screwing ourselves over?
OK Let’s look at what satiety is. It is a signal to tell you that you have just taken on enough fuel. I’m going to temporarily extend the definition to include “Not hunger” so as long as you are not hungry, let’s say you are perfectly satiated. And Let’s assume we’re all keto here and INSULIN is not taking energy off the table before our bodies can get to use it - or otherwise deranging us.
So let’s try a thought experiment. What happens if you get to satiety - you have the right amount of energy your body was hoping to get for the day … but then you keep on eating another couple of hundred calories?
Overeating after satiety
Obviously your body will suddenly have more fuel that it thought it was going to use. So there are 2 likely outcomes;
it will store some of that energy for a rainy day as body fat
it will take on some more energetic tasks and waste some of that energy
That first one is the only one that people who are obsessed with weight gain think about, but I personally find the second one more interesting. What happened? You just increased Calories in … what did your body do? It increased Calories out, your metabolic rate
Experimental evidence has shown that when we overfeed people TRYING to make them put on weight, it is very difficult to get most people to put on more than 10% of body weight. One prisoner volunteer in Ethan Sims’ Vermont overfeeding study ended up with a TEE over 10,000 kCal/day and unable to increase his body fat beyond 11%.
Undereating before satiety
SO let’s try the other end of the thought experiment, what happens if you knew what point satiety was but you intentionally stopped eating every day a few hundred calories short of that?
You will start to use some energy from storage
Your body will go into a budgetary crisis and furlough highly energetic processes, and conserve energy for essential services
I’m going to return to the first one in a minute, but that second one is the metabolic slowdown, starvation mode. So to answer the question given, satiation is the essential magic point above which you don’t slow down your metabolism, and below which you do.
Let’s say you eat to satiety but some macro calculator on a web site tells you you have to eat a few extra calories to get your fat calories in, or it tells you you have to stop eating before you hit satiety. You are following some magic calculation that that web site has determined to be perfectly appropriate for you. Do you think that web site knows more about your specific fueling requirements than your body does? It’s really unlikely now, isn’t it.
So this study looked into changing TEE based on changes in energy availability
They used liquid diets fed via tube to increase weight by 10% and and decrease weight by 10% and eventually 20%
And they found a 500kCal/day increase in TEE at a 10% gain and a 300 kCal/day decrease in TEE from a 10% body weight loss AND an additional 300kCal/day loss for a 20% body fat loss.
So why is CI:CO wrong if under eating draws down stored energy?
Well to explain that we have to go back to look at that first response to under eating satiety, and do another thought experiment.
Let’s say your body is budgeting to use 2400 kCal, but you only give it 1200 kCal - which could be a reasonable scenario in a low fat diet. The question your body fat needs to answer is can it deliver you that 1200 kCal to make up the deficit.
Infinite body fat
If we assume that you have absolutely no insulin in circulation which limits how much energy body fat can deliver, and we assume you have infinite body fat so the amount of body fat isn’t going to be a limit - then your body fat CAN deliver the energy on demand, and your TEE doesn’t have to change AT ALL … and you still draw down those 1200 kCal of stored energy, and hopefully you’ll weigh roughly 1/3 lb less every day.
Zero body fat
OK Let’s say now that you have zero body fat - this is a thought experiment, it doesn’t have to be reasonable. So obviously your body fat isn’t going to be finding you that 1200 kCal short fall. But you do have an alternate source of energy for emergencies. Protein. Lean mass. You can burn that for energy. So maybe your metabolic rate doesn’t have to drop to 1200 kCal. Let’s say you can make 600 kCal in budgetary cut backs, now you only need 600 kCal and you can draw down 150g of protein - roughly 1/3 lbs a day. You definitely don’t want to do this for too long because you won’t be able to … but in an emergency you have that option.
How about the real world?
So obviously no one has zero body fat or unlimited body fat (or zero insulin) - but we’re all going to be somewhere along that curve.
The rough calculation is you get about 31.5 kCal/day for every lb of body fat, and your insulin level, and how much weight you have already lost will all have an effect on how much energy you can get from body fat. So where you are in the journey will determine how much fat or protein your burn, and what happens to your metabolic rate.
That is the main reason why putting the brakes on calories in before satiation is a dumb idea, it lowers the amount of energy you use (starvation mode) while drawing down lean mass. This is obviously unsustainable and leads to yoyoing.
Eating to satiety turns out to be the way to burn body fat when your body will let you, and not lose lean mass instead, and not to feel horrible because your metabolic rate has dropped.
[sorry about the giant wall of text - hope it answered your question]
Since hunger is not really a problem for me when I am eating Keto, I do think I run the risk of operating for extended periods at too much of a caloric deficit and potentially slowing down my metabolism, when I eat to satiety.
I currently eat protein to a target (including the fat that naturally accompanies high quality, real food protein sources), then I use cold hands and or feet as a barometer of whether my energy intake is adequate to support my metabolism. I take cold in the extremities as a signal from my body that it is conserving energy, and I increase my energy (fat) intake. It surprises me how quickly a relatively small amount of fat will warm up my hands and feet.
A very good advertisement for “Know thyself”. Bravo.
We are all different. How much energy we can get from body fat will depend on how much fat we have, how much insulin is in circulation and how insulin resistant our adipose tissue is.
But some people have real problems hearing satiety signals. Dr Phinney says it takes 6 months before you can accurately judge satiety. Tim Noakes says some 10% of people (often women) never get to that point.
“In lay terms,” Moss says, sensory-specific satiety “is the tendency for big, distinct flavors to overwhelm the brain, which responds by depressing your desire to have more.” To avoid this, successful junk food products like Coca-Cola and Doritos consist of “complex formulas that pique the taste buds enough to be alluring but don’t have a distinct, overriding single flavor that tells the brain to stop eating.”
So, I fast frequently so have only temporarily gained back 5 of the 29 pounds I have lost. So I think it’s legit fat loss. I just need to figure out my happy place once I burn through the next 25-40 pounds of fat. Not sure where I will land weightwise but intend to continue frequent fasting. Fasting eliminated all the symptoms of my thyroid disease and I really enjoy fasting. I think this maybe the piece of the puzzle that was confounding me. Thank you @richard for taking the time to make this clear. You guys have really provided me with so much information. I was lucky to not have type 2d despite gaining 90lbs during pregnancy and remaining overweight for a decade, genetic luck of the draw. Keto and particularly fasting have really helped me take control of my weight and helped eliminate all symptoms of my thyroid autoimmune disease.
Ok that’s fine then. To me that’s the true test of whether a fast is worth the time, can you eat normally afterwards and maintain a lower weight. I think there is value in periodic overeating as well, to tell the body that there are times of plenty as well as times of scarcity. Overall though I think Jason Fung has propagated too much terror over the idea of metabolic slowdown and it’s not mentally healthy for many to be thinking about this all the time.