Ketosis & Calorie Deficit

(Chris Holmes) #1

I posted this as a reply to an old thread, but no response, so posting new here…If there are any biochem folks out there who can help me understand why a body in full ketosis would still need a calorie deficit to lose fat. I get that restricting carb intake will lead to lower caloric consumption, but I thought the science behind keto, was that the metabolic changes your body goes through when in ketosis, causes burning of fat stores for energy, which makes me wonder whether the weight loss is actually due to burning fat, vs just consuming less calories than your TDEE. It would be interesting to see a study that compares people in ketosis eating enough calories to match their TDEE vs people who are not in ketosis eating a 20% deficit to their TDEE. Interested in the science behind the explanation. Thoughts?

(Allie) #2

Personally I don’t believe it does and I’ve been feeling much better since I stopped calorie counting.

(Lonnie Hedley) #3

Agree. As long as I keep pretty strict with my macros (80% fat, 20% protein, handful of carbs), I see no difference from 1800 calories to 2500 on the scale.

(karen) #4

I think there may be two different questions wrapped up in this.

If you take in more (fat) calories than the charts say you need, ketosis may be able to excrete them or somehow burn them so that you don’t gain weight, at least up to a certain point. (maybe indefinitely, from some people’s n=1 experiments).

OTOH, if you want to Lose weight, I think you’re going to have to input fewer calories than your body can burn. But in ketosis, it seems your body can burn / excrete a lot more. In other words, you can take in 2500 calories and still have enough of a deficit that your body’s dipping into your fat cells to make up the difference.

I would guess that there would be no reason for your body to burn its own stored resources if it’s truly overloaded with external energy, but “truly overloaded” appears to be an incredibly subjective thing.

(Robert C) #5

Unfortunately, I do not have the science (other that what Dr. Fung says).

Here are some ideas that might clarify some things.

Let’s say you eat 2000 calories of pure fat as part of your diet for a day.
If your insulin is very low for the entire digestion window, then your body isn’t going to pay much attention to the fat is running through it.
If your insulin is high, your body will want to preserve existing fat and store new fat - so will keep what it can of the 2000 calories.

That is the explanation I’ve generally seen - the same number of calories of fat produce a very different storage result based on insulin level.
This is why Type-1 diabetics (before we discovered insulin) would simply whither and die - regardless of calorie intake (Type-1 diabetics cannot produce insulin).

But, your request seems to be being asked from the human-as-a-machine point of view.

It seems to assume that a 2000 calorie intake of fat must be fully assimilated and then the body must account for the new energy with a “burn” of that amount of calories before there is an overall deficit.

That is the fallacy - without the digestive enzymes of a termite, I cannot consume wood and produce energy to keep me going.
10,000 calories worth of wood chips can keep a large colony going but I will whither and die.

Ketosis keeps insulin very low so, depending on how low it goes - your body will ignore higher and higher amounts of fat.

(So much bacon . . . so little time . . .) #6

Well, the short answer is that it does—and it doesn’t.

As Dr. Westman put it, “Calories do matter, but you shouldn’t count them.” You are right that a fat-adapted body can use both dietary fat and fat stored in adipose tissue to meet its energy requirements. The level of caloric intake is not completely irrelevant, but there are documented cases of people consuming 3000 or even 5000 calories a day and still metabolizing stored fat. On the other hand, Dr. Phinney says that, in his experience, most people embarking on a ketogenic diet spontaneously limit themselves to about 1500 calories a day by eating fat to satiety. And of course, as we lose that extra fat, we will eventually find ourselves getting all our daily expenditure from our daily intake. Dr. Phinney’s point is that by eating fat to satiety, our bodies will guide the process, and we will hardly have to think about it. The key to the process is, of course, keeping our carbohydrate intake low enough to avoid stimulating insulin production, since insulin is the hormone that promotes the storage of carbohydrate and fatty acids in the adipose tissue.

Another factor people often aren’t aware of is that if we deliberately skimp on calories, the body is likely to react by lowering the basal metabolic rate and hanging onto its fat store; whereas when we give it enough calories, it will ramp up our metabolic rate, burn off excess fat, and even find ways of wasting energy.

So the upshot is that an intentional caloric deficit is not a good idea. Much better to eat fat to satiety and let the body determine how much energy it needs. I guarantee you that our ancestors a million years ago never counted macros, lol!

(Chris Holmes) #7

All good points here. I am living proof of what Phinney says regarding the spontaneous limitation of caloric intake. It is very difficult for me to consume more than 1850 calories per day. The first 2 weeks I was around 1500, and for the last 5 weeks, it is a steady 1850. I am always satiated and never crave anything anymore. That being said, my TDEE is around 2800, which means that I am consuming a 950 calorie deficit per day (34%). If someone who was not in ketosis did 30 min HIIT workouts 5 days per week like I do, and consumed a 34% calorie/day deficit, they would most certainly burn fat/lose weight, without being in ketosis. I guess the short answer to my question is, that if you add ketosis to that same person, they would burn fat more efficiently, and potentially reach their goals faster?

(So much bacon . . . so little time . . .) #8

Not necessarily, given the body’s reaction to caloric deficits. Such a person might find their body shutting down non-essential processes in order to conserve energy.

In ketosis, and given an adequate supply of calories (as I understand it, this part is just as crucial as being in ketosis), the body should definitely respond by disposing of excess fat deposits.

I’m not sure “would burn fat more efficiently” is the right way to put it. Depending on the insulin level, the body is either burning fat or storing fat. I’m not sure that, once fat-adapted, there are degrees of “efficiently burning” fat. But please don’t read too much into this paragraph; it occurs to me that I may just be hung up on the words and not adequately conceptualizing the reality. You could very well be right.


Very glad for this post. I had this same question as I try keto for the first time. I dont want to restrict my calories too much as I worry about lowering my BMR. I thought the beauty of keto was that I can keep up total calories per day so long as those calories are from fat and be in ketosis but I am reading so much about the necessity of a caloric deficit for weight loss even with keto and was confused. I can’t say that this entirely clears it up for me because it raises more questions now. For instance, if fat adapted and you don’t need a caloric deficit to lose stored fat, how would you stop your selffrom losing fat all together when you’re in maintenance mode?


Your appetite should adjust upwards as you get leaner. Some people continue to lose but the vast majority find their sweet spot naturally.


That is great to hear. I was hoping for this answer!


The best answer is to try it for yourself for 1 month each.
Try upping your calories, and see what happens TO YOU.
Then try reducing them, and see what happens.

Be sure to measure what your eating so you have the best idea what you’re eating.

You will get to know very quickly, which is best for you.

(So much bacon . . . so little time . . .) #13

If you eat little carbohydrate, a moderate amount of protein, and fat to satiety, your appetite level will regulate your caloric intake. This vexed question of caloric restriction is backwards, according to the insulin/hormonal model of weight storage and loss. Dr. Phinney says that his team found that, on average, people beginning a well-formulated ketogenic diet who ate fat to satiety automatically ended up eating around 1500 calories a day, making up the rest of their energy needs from stored fat. As they lost weight, their caloric intake automatically increased, to the point (eventually) where they were getting all their energy from their food intake, because they had no excess stored fat left. The point is, however, that they did not restrict their calories intentionally, they just let their appetite determine how much to eat.

So many people come to the ketogenic diet in order to lose weight that we tend to lose sight of the fact that the ketogenic diet is not a weight-loss diet, it is a weight-normalization diet. It just so happens that as a society we’ve blundered our way into a situation where most people are obese, so we see a lot of fat loss.

There are hormonal mechanisms that regulate fat as a percentage of body weight. The mechanisms evolved for good reason, and we can trust them to reassert themselves when we stop distorting our health with a gross overabundance of carbohydrate. Normal men (from before the dietary guidelines) have about 12% body fat, whereas normal women (ditto) have about 21-23% or so, (Women need more fat as a cushion during gestation and lactation, for example.)


Thanks Paul. I think that helps to understand this process better. I really wanted to know if I needed to meticulously count all my calories being on keto, and I’m so glad that I can let my body dictate this for me. After my first 20lb loss with fasting and logging/measuring everything to be in a weekly deficit, I am so very tired of all these calorie numbers that circle my brain daily… I do like fasting and intend to keep that up, but for my last 15 to lose, I really was hoping to find something that I don’t have to be so obsessed with counting calories. Before everyone gets all heated up again. I DO understand that calories matter and I just won’t need to freaking measure, weigh, log, panic if there’s no nutritional label or the data base doesn’t have it. That’s ALL I mean. I need a mental break it from it all.

Thank you all sides for your POV on this topic. It’s helpful to hear all sides. My take away is that calories do matter, but not to a point where I need to track it the way I used to. I will makes sure those calories come from fats and let my body normalize so I can go on to be a better intuitive eater.

(charlie3) #15

My view is calorie counting is more important if you’re trying to control body fat by eating smaller portions of a SAD diet. This approach is infamious for not working in the long run because you’re likely to be hungry all the time. I’m currently at 11-12% body fat, no reason to go lower.

What I do now is limit meals to 12 times a week, lunch and dinner and zero snacks. I eat about 350 calories per day more than I need for maintenance then eat nothing one day a week to zero out the excess calories. If I want to reduce body fat I’ll eliminate the excess 350 calories and still eat nothing one day a week which should burn off about 1/2 pound of body fat. I never want to gain or lose more than 1/2 of fat a week. I figure that’s a reletively gentle change if I’m fat adapted and doing plenty of exercises that create a demand for energy. So may be what we’ve learned is that lower carbs at fewer meals plus fasting days are the best way we know right now for controling body fat and may be even improving other health markers.

So I’m counting calories right now with Cronometer for meal planning, for what it might teach me about long term trends and particularly for tracking micronutrients. If I’m going to all this trouble I might as well be confident that the micro’s are covered, not just the macros.

(Robert C) #16

This sounds like an excellent maintenance plan with a guaranteed weekly zero out of glucose and flexibility to handle social engagements (assuming you are not too rigid about which day of the week is your fasting day). I am going to steal it when I get to maintenance!

(charlie3) #17

My view is the ability to control eating times is a kind of fitness, it needs to be developed like strength or cardio fitness. I suspect control over when and how often I eat rivals the importance of what I eat and activity. So I keep to my eating times and weekly day-long fast regardless of maintaining or losing body fat. I’m writing this on a Saturday, the day I don’t eat. My resting metabolic rate is between 14-1600 calories. Today I will walk 60 minutes at 60% of max heart rate and ride 80 minutes on my stationary airdyne at +70% of max heart rate. Those two activities burn another 1,000 calories. So my no-eating day probably consumes 2600 calories. In return I can eat +400 excess calories per day for 6 days, an easy tradeoff for me.

(Robert C) #18

Thanks for the extra details.

I like the eating pattern but I think I would be a little more reactive on the other things (where you have calculated all of the numbers for yourself).

I assume the body is always adapting so metabolic rate moves around, body becomes more efficient when regularly walking or running etc.
So, I’d probably stick with what you wrote earlier

Seems like the best way to do this is to fast a little more if I have gained and enjoy easing off of fasting if I am down.

Even anticipate vacations and holidays getting weight down a bit earlier with fasting (much more fun than thinking about how you’ll have to fast weight off afterward).

All the while - some form or other of exercise - but mostly to keep some muscle and keep joints happy (vs. for weight loss).