Why would my metabolism slow down if I’m getting cals from fat stores?


Specifically, which signals to where that would slow metabolism if enough energy is supplied via fat + diet? Are you suggesting to eat beyond satiety just to meet a calorie goal?

True, but at one year in there is still a significant fat mass in this case. Now, if someone were intentionally limiting calories, even though hungry, to continue losing weight that would be a problem.


I’m so confused. I don’t know why I thought my dumb brain would get it. Whatever, as long as it works I’ll just KCKO.

Thanks for trying y’all.

(Ashley) #23

Sharon, I just eat til full. I do not track. Some days I’m sure I’m under 1000 cals. Other days I may be 1700 cals. I just make sure I’m satiated. Your body will adjust especially if it needs to burn calories! I don’t stick to a amount to eat, I think eating different amounts different days, keeps my body confused and also keeping it out of starvation mode as I’m not constantly at a large deficit!


I am grateful for your question because I think I have been overdoing the calories for the sake of not restricting and it is absolutely not working for me. I have lots of my own fat to burn, nearly 3 months in strict Keto with almost no weight loss, the only tweak I have left, I feel, is to stop worrying about under-eating calories and see if any loss happens with that change…

(Give me bacon, or give me death.) #25

Dr. Fung explains it this way: if there is caloric input, the body matches energy expenditure to intake. Give it enough, or more than enough, and it will increase metabolism to match. Try to manipulate fat loss by reacting intake, and it will slow down the metabolism, making it necessary to cut intake even further. The Biggest Loser contestants did themselves permanent damage this way. This operates even in a low-carb milieu, which is required for fat loss.

But in a low-carb milieu, the leptin signaling to the hypothalamus is no longer being blocked by insulin, so the brain can set the appetite to a level at which both dietary and stored fat can be metabolized. Hence our advice to eat to satiety, so the body never goes into famine mode. But when we fast, Dr. Fung explains, there is no caloric intake to match, so the body simply switches fuel tanks, as it were, and fuels the metabolism out of the stored reserves; i.e., fat.

Makes sense, no? When we have a Mastodon carcass handy, we feast. When it runs out, we go out, fasting, and hunt another, metabolism running at full speed. But when game is scarce, we eat whatever is to hand, and the caloric restriction is the signal to the body that times are hard, and it needs to conserve resources, to get us through.

(Alec) #26

I think you have asked a fantastic question and I am not sure we have a great and clear answer right now. I know I don’t. I have often wondered about the low calorie vs fasting thing and the differences to metabolic rate that we think/hope happen when we fast vs when there is severe calorie restriction.

But I think we do know that the body does react to lower intake by reducing metabolic expenditure. So it happens, we just don’t know the exact mechanisms. I am pretty sure that @Karim_Wassef and others experiments have shown that the metabolism definitely drops when we eat lower calories, even on keto.

The encouraging thing though is that it seems our metabolisms are pretty resilient unless you have done something crazy like Fastest Loser competitions.

(Karim Wassef) #27

Let’s try an analogy. Imagine this:

You have a coal furnace that give you energy to do stuff.

You have one guy who can shovel coal into it from a huge pile. Just ONE guy.

You have 10 guys who can shovel coal into it if it comes from the outside… fresh coal is so special that the big boss put a whole team on it.

Now. There’s a supervisor. This guy is nasty and he checks all the incoming coal… if he sees any gray chunks of coal (instead of black coal), he chains up the ONE guy who can shovel coal from the big pile… even if all the new coal is finished… even worse, the furnace can’t handle more than one chunk of gray coal a day… so he just tells those 10 guys to move ANY incoming coal into the pile for that day.

Now… let’s say you don’t have any new coal coming in. All you get is one guy shoveling coal from the big pile… the oven gets cold even if you have a mountain of stored coal… you’re just going to have low energy.

Now… let’s say you get some new coal and it’s the gray kind. The ONE guy gets chained up and can’t shovel any coal from the pile AND you only get one piece of gray coal for energy… so if any new coal comes in, it adds to the pile. Now you really have no energy…

Now… let’s say you get some new coal and it’s the black kind. The team can keep shoveling it in and the ONE guy can shovel in old coal from the pile too. Now the pile gets smaller and you have TONS of energy.

The black coal is fat

The gray coal is carbs

The ONE guy is how your body processes it’s own fat.

The 10 guys is your digestive system and the liver.

The huge pile is your body fat.

The new coal is food.

The furnace is your body’s Metabolism.

The supervisor is insulin.

The big boss … leave it up to you to decide.

(Alec) #28

But shouldn’t this mean if you are strict keto then you wouldn’t lower metabolism if you ate very low calorie chronically? Doesn’t Sharon’s question still stand?

(Karim Wassef) #29

No. Strict keto is the equivalent of such a small nugget of gray coal that the supervisor misses it.
Then you get plenty of energy and burn your own fat.

The only time this “could” reduce energy is if the sum total of coals from the ONE guy shoveling from the pile + the total of black coal from outside is less than your body has been used to using.

Basically, your body fat is available as food = satiety while burning your own fat

(Alec) #30

So you’re saying you don’t think there is a metabolic slowdown if you eat chronically low calories if you are strict keto? I didn’t think that’s what your data said?

(Karim Wassef) #31

I was fasting. Yes - fasting lowers metabolism.

Eating keto is about consuming fats from the outside + maximizing fat use from the inside. The dietary energy intake is reduced, but the total is unchanged… so no drop in metabolism.

That’s why keto is amazing.


Chronically low would have to be defined in context. The original post 1200 cals doesn’t sound unreasonably low for someone in active fat loss with adequate body stores.

If there’s very little hunger, perhaps a 24 fast would be a good next step, followed by a buffet.


It isn’t about how much energy is being supplied via fat stores. It’s the lack of energy being supplied by intake.

No. I’m not sure what the point of that would be.

It doesn’t have much, if anything, to do with how much of those emergency fat stores you have. It’s the under eating and tapping the stores that causes the down regulation.

I think this is wise.

I think there is. I wasn’t aware that keto was protective of this mechanism. Though I’m not sure we have enough studies to really know. We know that fasting is protective and prevents down regulation, but that’s it, as far as I know. (Which, honestly, is very little, so…)

(Empress of the Unexpected) #34

Again, I’m usually 600 to 800 calories a day. No problems for 61 years. Except when I was eating carbs. I went from 145 to 108 on keto. I think a lot of people on here are trying to justify carbs. If you are under 20 grams, you will shrink big-time.

(Alec) #35

Rather amazingly, this exact scenario and question was discussed by the Original Dudes in the latest 2KD podcast. Richard’s view was that on a low cal keto diet your metabolism would not drop as long as you had low insulin and you had enough bodyfat.

(Eric - The patient needs to be patient!) #36

The low insulin is key.

I think for people that are still very insulin resistant the metabolism can drop with fasting. I listen to my body. I’ve had days post fast where my hunger signal said eat more fat and protein. So I did and did not gain. In fact I lost weight during the post fast re-adsorption phase. As I continue to improve my insulin response and lose more weight, my post fast eating signals say eat less. And I do. As a proxy for fasting insulin testing I see my morning (fasted) BG levels dropping from 130 to 85 to 90.

At least that is how I am interpreting the eating / hunger signals. It is working for me. My energy stays high, I’m not cold (except during EF days) and I’m losing weight at 1.5 to 2 lbs a week.

Exercise seems to help at least that is what the experts say. Resistance training improves insulin response. 9 days out of 10 my exercise energy and strength are fantastic.


Tapping fat stores is the point of keto. The down-regulation is if there isn’t enough total energy available. Any specific information to the contrary?

(Eric - The patient needs to be patient!) #38

Carol I think you have boiled this down to the essential understanding.

(Bunny) #39

Here is my quick run down conjecture (theory or hypothesis) on this:

Ghrelin, leptin axis imbalance and glycogen being replaced before it can have enough time to be in a depleted state (takes time for the metabolism to adapt to this i.e. slows down) before the body will start burning body fats (lipids) and then higher than normal cortisol trying to put visceral fat back around the internal organs and into the subcutaneous fat stores because of attempting to restrict calories or carbohydrates (20 grams?) too fast or to soon causing metabolic shock rather than doing it slowly, in other words the slower (and I do mean real slow) you go into this restricting carbohydrates; the faster your metabolism will become?

Adapting (hormesis; metabolic stress tolerance) or adaption onto the ketogenic diet is something that really gets over-looked:

Basal metabolic homeostatic stress point and support structure analogy:

  1. If you put too much stress on a dry thin wooden stick depending on the support points at once you will snap it in half?

  2. A wider support distance you will snap it immediately?

  3. Move the two support structures inward the stick will give more resistant before you can snap it.

That wooden stick is your metabolism?

Another way to look at is, let’s say that 20 grams of carbohydrate is a rubber band pulled back as far as it will go and it is extended on your arm by your other hand and you have it pulled back as far as it will go, it’s going to hurt when you let go of it? That is what happens with the speed of the metabolism on an individual basis? One person may restrict carbs and weight comes flying off, another person tries it and nothing happens?

(Brian) #40

I’m with Paul on this one… Dr. Fung has spent a lot of time on this one. I tend to think he has a pretty good handle on fasting vs calorie restriction.

In my natural state, I tend to agree. I’ve never really been much of a “grazer”. If I don’t want to eat, I don’t want to eat a little either. If I want to eat, I want to eat a substantial meal. The idea of a “snack” is kinda foreign to me. (And it appears that’s a blessing!) I’m way, way more inclined to skip a meal completely than to eat a very small meal. And mostly, it’ll be the habit that will talk to me the most. Once I’m past the routine of eating (cause it’s time) and have moved on to the next project in my day, I’ll likely forget that I even skipped the meal.