Is there such thing as too much of a calorie deficit?


I’ve been reading competing advice on different sites, so I was hoping to get some clarity from you fine folks.

For someone on a keto WOE, fat adapted, how much of a caloric deficit is too much? Or is that even a concern?

I’m about 248 lbs, 27.3% body fat. So if I don’t consume anything, my body should be able to draw 2,166 calories from my body fat (248 * .273 * 32 ).

I do IF, and eat either TMAD or OMAD. Calories consumed go from 2,000 - 3,300, depending on number of meals eaten and activity that I do for that day. I weight lift every other day and walk/stationary bike the off days, and most weight lifting days. According to my FitBit, calories burned range from 3,000 - 4,300. So some days I might have a deficit of over 1,000 calories.

I feel fine now that I’m upping my salt intake. I don’t feel hungry and my mind is clear.

My main goal is to lose fat mass, but I’d also like to gain muscle mass. I’m tracking everything and so far so good. I’m losing fat while gaining muscle. I just want to make sure that I’m not doing anything wrong. I don’t want to go on vacation (lowering my daily activity) and then my body takes that opportunity to put on 10 lbs.


I have another related question, not sure if I should make a new topic.

On days where I fast for 24+ hours, and therefore consume 0 calories, I might burn 3500 calories as a result of activity. If I can only get 2,166 / day from body fat, where does the rest of the energy come from? I assume that I have depleted glycogen stores since I’ve been eating keto for so long. Is this where autophagy kicks in and the body starts burning those old cells/proteins to make up the deficit?


You should focus on macros, not calories.

First, set your macros, keeping in mind that the proteins macro is a lower limit, while the fats and carbs macros are upper limits. Your proteins macro should be based on lean body mass and activity level.

I see keto as simply “Minimal carbs. Adequate proteins. Fats as needed (for satiety).”

So, two priorities:

  • You need to keep carbs low to stay in ketosis.
  • You need to make sure you get enough proteins. Your body needs them. Being significantly low on them over an extended period can cause the body to get it elsewhere. That may mean break-down of muscle tissue. Not good.

After that, ideally, it should be hunger that determines how many fats (and thus calories) that you need to be eating, because stored body fat can make up for fats you’re not eating. But leaving yourself hungry all the time means keto won’t be sustainable.

Forcing calories to be far too low (i.e. “crash” dieting) is not necessarily a good idea. A follow-up of some of The Biggest Loser contestants found that their crash dieting resulted in the average BMR reducing from 2600 to 2000 over the 14-week competition. Six years later, the average BMR was 1900 and almost all had regained most of their weight and body fat percentages.

The dogma says a 25-30% deficit is OK for someone morbidly obese, but otherwise 20% or so. Not sure if any science supports those levels.

(Give me bacon, or give me death.) #4

The human body has spent the past couple of million years adapting to cope with a wide variety of conditions. On a well-formulated ketogenic diet, we do not recommend restricting calories, for two reasons. First, the body’s hormonal response to the types of food we eat is far more significant than the motto “a calorie is a calorie” would tend to suggest. Second, the body seems to interpret reduced caloric intake as a signal of famine, and in such a case it hunkers down, slowing our metabolism and hanging on to our fat stores, in order to get us through the famine.

So the point of restricting carbohydrate is to reduce serum glucose levels to the point where insulin can safely drop. Since insulin is, among many other things, the primary hormone involved in the storing of fat in adipose tissue, low insulin levels are desirable from the point of view of losing excess stored fat, as well as from the point of view of metabolic health. Then the point of our advice to eat to satiety comes into play, because we don’t want to trigger the famine reflex. The lowered insulin allows our body’s appetite and satiation hormones to function properly, whereas elevated insulin levels block key receptors in the part of the brain that regulates our appetite, leaving us feeling perpetually hungry.

A corollary to the maxim “a calorie is a calorie” is the advice to “eat less, move more.” Both of these maxims fail to account for the body’s hormonal response to the foods we eat. As Dr. Jason Fung explains, the thinking that all we need to do to lose weight is to create a caloric deficit fails to achieve its goal because it describes the situation as a “one-compartment” problem, whereas what we are really dealing with is a “two-compartment” problem. If we were truly dealing with a one-compartment problem, it would not be possible to shed excess stored fat while simultaneously building muscle and bone. The one-compartment model says that all food is either metabolised or stored as fat, leaving the possibility of increasing lean mass out of the picture.

Fortunately, a well-formulated ketogenic diet eaten to satiety provides the proper nutrients in both quality and quantity. For building muscle, we need foods rich in the essential branched-chain amino acids; for shedding excess stored fat, we need foods poor in glucose—in other words a low-carbohydrate diet. To build muscle, we also need energy, which in the absence of carbohydrate must come from fat (which has virtually no effect on our insulin level). When insulin levels are low enough and the appetite hormones are properly functioning, we automatically eat at a level that allow both our dietary fat and some of our excess stored fat to be metabolised. And to avoid slipping into famine mode, we need to consume enough calories to permit the body to freely dispose of its resources. The best way to ensure that we are not stinting on calories is to eat to satisfy our hunger.

Interestingly, fasting does not trigger this famine mode. Instead it switches the fuel source from food intake to fat reserves, which is why fasting ketosis and nutritional ketosis are such similar states. As I understand it, the withdrawal from fat reserves matches the energy needs of the body, up to the limit of the maximum number of calories that can be withdrawn from those reserves. If the maximum is less than the energy need, then the metabolic rate must drop to compensate for the shortfall.

(Michael - When reality fails to meet expectations, the problem is not reality.) #5

(Bunny) #6

Read this (which almost explains everything any one could ever know on the subject; if your not losing body fat and gaining muscle from lifting then your doing something wrong?):

Brady Homer: “…While overall protein balance may be more important for muscle protein synthesis, some data show that consuming 20 - 30 grams of high-quality protein after exercise will maximally stimulate protein synthesis. Make sure to include at least 2 grams of leucine—the most potent driver of protein synthesis. …”

“…However, when studies compare protein ingestion alone to a combination of protein and carbs after resistance exercise, there is no difference in muscle protein synthesis.10,11,12,13 Long story short: the carbs don’t seem to be adding anything extra.This is probably due to the fact that the amount of protein ingested is enough to raise insulin levels and activate mTOR. More insulin doesn’t necessarily mean more protein synthesis, in this case.10,11

This might silence any argument against using the keto diet to build muscle. But another argument against keto for athletes has to do with glycogen (stored glucose) in muscle.

If glycogen stores are low during exercise, this could compromise energy availability and limit performance. Not something that any athlete wants. However, this may be more of a concern for athletes involved in endurance activities where glycogen depletion becomes an issue. Athletes in sports involving heavy lifts or bodybuilding might not experience negative effects from low glycogen.

However, the data don’t support that glycogen levels are reduced on a ketogenic diet—at least after a sufficient period of adaptation occurs.

In fact, keto-adapted athletes who were compared to athletes consuming around 600 grams of carbohydrates per day actually had similar levels of stored muscle glycogen. After exercise, the keto-adapted athletes were also able to replenish their levels of stored glycogen just as well as the carbohydrate-consuming athletes—despite consuming about 75% less carbohydrates during that period.14 Something happens to keto-adapted athletes that allow them to maintain glycogen levels at a high level. But what?

Maintenance of glucose and glycogen levels in the body in the absence of carbohydrate consumption can occur through a process known as gluconeogenesis, or GNG for short. GNG is a process that our body uses to create glucose out of non-carbohydrate sources—mainly amino acids and glycerol from fatty acids. …” …More

These few paragraphs are just mind blowing?

Kudos✌️to Mr. Brady Homer!

Mystery solved?

Only problem is you loose the anti-oxidants benefits in Whole Food carbohydrates if your ok with that and want to do strictly carnivore??

Oh yes if your going to “fast” don’t do it too much or you will end up taking your newly developed muscle with it?


Thank you for the responses folks.

I want to be clear that I am not keeping a calorie count and stop eating when I hit a certain threshold. I do write down what I eat (therefore know what my caloric intake is approximately), what my workout is, weight, BF % etc. When I have a meal, I eat until I’m no longer hungry. I can probably have a little more of something if I wanted to, but I’m not stuffed. I think that’s a good place to be. I think that consuming over 3,000 calories would be satisfying and shouldn’t trigger a starvation response, even if my calorie deficit for the day is over 1000 calories, but please correct me if I’m wrong.

I don’t snack. I have one or two meals a day, and they are full 1.5k+ calorie meals, with lots of fat and a good amount of protein.

I do watch my macros. I keep carbs low, usually 25g or lower. On some occasions after a good workout, I might indulge in some blueberries and nuts which ups my carb count, but I’m still losing weight and improving on my body fat percentage.

Keeping this in mind, is it safe to say that I am not doing myself any harm?

Not sure if this is helpful… I still have some ketostix, and they show at least 1.5 mmol when I wake up in the morning. They usually go deep purple if I fast for a day.

I have read Dr Fung’s books, the Obesity Code and the Complete Guide to Fasting. Very good reads!


I’ve heard about leucine but haven’t read anything about the advantages to taking it.

Interesting paragraphs that you have there. I will read up the full article later on tonight. Thanks for sharing.

(Give me bacon, or give me death.) #9

I’m not sure what you mean by saying that your calorie deficit for the day is over a thousand calories, when you are eating 3000 calories. Isn’t that difficult to achieve, or am I missing something? (I wouldn’t be surprised to find it was the latter.)

In any case, it really does sound as though you are listening to your body and are therefore almost certainly fine. A ketogenic diet can sometimes lead to surprising results. So much of what we consider “normal” is the result of studying carb-burners, and we are finding that normal for ketonians can sometimes be quite different.


Many people need more than 4000 kcal energy per day, there are some big or active folks… I am a short, not muscular, not very heavy woman but I surely used up more than 4000 kcal on some exceptional days with much walking… :smiley:
Some people frequently uses 10000 kcal too. Well that’s hardcore but an experienced one in good form can do it if they do some strenuous activity (where even 1000 kcal/hour may be realistic) for many hours (or a somewhat lighter activity for 20 hours)… Of course, it’s not an every day situation but some physical competitions fits the bill. Big muscle loss can happen there but they have little fat to lose and eating enough may be problematic, it depends.


not a concern!! if you are eating well, feel great and all.

you are trying to ‘do numbers’ down to specific bodily functions and more and on our way of life like keto and I am zero carb…all that just dumps out. We drop all the BS ‘dieting crap to the wayside’ of ‘hit this number’ which is absolutely unreal and useless.

Just eat well. You know you and how you need to roll on a daily basis. Listen to your body and if you always eat on plan and do your activity based on your energy level etc it all balances out as we heal thru our eating/activity change.

It is so simple yet we are ‘told’ it is not…yet it really friggin’ is :slight_smile:

you won’t put on 10 lbs on vacay if you eat on plan…you might if you don’t eat that and go rogue into carby junky food crap :wink:

how long into this lifestyle cause your ‘’‘I think that consuming over 3,000 calories would be satisfying and shouldn’t trigger a starvation response, even if my calorie deficit for the day is over 1000 calories, but please correct me if I’m wrong’’’’’ is making you doubt your plan in that your keto plan will work if you let it yet with all the ‘diet baggage’ we carry into this new way of life can screw us up a lot.

forget the numbers to this small level of control you think you have cause a physical body will never and not ever contort to your whims and ‘what they said’ should go down. I know, I been there done those thoughts and ‘tried to live by specific numbers’ and I say it will never work in any way ya think ‘it should’ as we are told.

We are so individual. So different in med situations, age, environmental life experiences, activity and more so the ‘one size kcal and numbers they say works, never does’ so DO YOU thru it all. Eat your keto as you need and thrive is best one can do and in the end, yea that actually works if we allow it :sunny:

I say eat well, go by your body, enjoy your keto plan and don’t put that emphasis on 1 kcal will make or break your life. It isn’t that way and won’t ever be…….so just some thoughts on all of it

(Bunny) #12

The bigger you are the more calories you burn from information I see scattered across the internet. It is estimated (Robert Sapolsky, Stanford professor of neurology and neurosurgery) that the human brain can burn 6,000 calories a day trying to solve complex problems without even moving the body very much. That’s just the brain by itself.

From The Book “The Math Diet” by Julius Kieser

(Vic) #13

I used fitbit when it came out, It said I burned crazy amount of calories when I was worked out

Too much in fact there is no way its accurate


I am a bigger boy than average, 6’4". If FitBit is to be believed, I typically burn 4,000 calories a day with my current activity level. So if I eat 3,000, the deficit would be 1,000. Roughly of course.

It doesn’t sound like this is an issue, which gives me a sense of relief! Thanks folks.

My concern came from having been on low carb diets in the past (high protein, low carb) , losing a ton of weight, then gaining it back again over years. Then continuing the cycle, again and again. I read about why Atkins type of diet isn’t sustainable and keto is, but I still have that fear that Fat Mavro might come back if I’m not careful or if I’m not doing this right.

I’ve been doing clean keto since December 2019.


I have another related question, not sure if I should make a new topic.

On days where I fast for 24+ hours, and therefore consume 0 calories, I might burn 3500 calories as a result of activity. If I can only get 2,166 / day from body fat, where does the rest of the energy come from? I assume that I have depleted glycogen stores since I’ve been eating keto for so long. Is this where autophagy kicks in and the body starts burning those old cells/proteins to make up the deficit?


Your body doesn’t care that you eat keto nor does it understand that. All it knows is that if your not eating, than you must be too stupid to hit something in the head with a rock and eat it. So if you keep it up it’ll start preparing to slow down. With TMAD and OMAD as long you’re ultimately getting your cals in you should be ok.

Since you have a good amount to loose make sure you’re getting enough protein and have your body composition checked a couple times a year. Don’t assume it’s only fat you’re loosing. I lost a ton of muscle and I’m still fixing it now. In the muscle dept I’m pretty much fixed but my RMR still sucks.


I just got my DEXA scan confirmed for this Saturday. Last one was in mid-February. I hope to see a good positive progression.

I think that I have been doing a good job at keeping my protein up and seeing the results in being able to lift more from session to session.

(Give me bacon, or give me death.) #18

If necessary, your body can adjust its metabolic rate to compensate for reduced intake, whether that intake is from food or from stored reserves. It can also ramp up the metabolism when intake rises.

I would take the figures with a grain of salt, because of inherent inaccuracies of measurement, together with the fact that our caloric figures per gram of carbohydrate, fat, and protein are only rough averages. And don’t forget that food calories are actually kilocalories. If I recall correctly, the caloric values of a gram of protein and a gram of carbohydrate are slightly more than 4(000), and the caloric value for a gram of a given fatty acid ranges from about 6(000) to around 10(000), depending on the fat in question. (I may be making up these numbers, so please don’t quote them. But the idea is correct in essence.) Add those facts to the difficulties of accurately measuring metabolic expenditure, and the margin of error becomes quite considerable.

In any case, it would appear that we evolved to thrive on periods of feasting alternating with periods of fasting. And the fasting periods are when our ancestors would have been out scrounging up the next mastodon, or whatever, to feast upon. So whatever the availability of energy while fasting, it is apparently enough for us to survive and thrive.


I know. This was me.
there is only one way for this not to repeat. Hold plan.
Stay on plan no matter what. When we ‘walk that line’ of I ‘can eat this and be ok’ then we carb creep up and up and boom…yea so many of us did this.

Lifestyle change. Key words here and must be respected or we are in a nasty vicious cycle we all hate and have done.

There is no magic to any of it. Stay on plan. Eat plan. Treats must be extremely rare and almost non-existence for many of us. Thing is every single maintainer person who succeeded long term says one thing…they eat almost every single day on plan as they did to lose the lbs. There is nothing after that. How you eat to lose it all is where you need to be to keep it off.


That was my issue. “A piece/slice/slab of X won’t hurt.” But then that turns into 2X then 3X, then every weekend, until it’s a regular thing.

I find that I’m pretty good at saying ‘no’ to things but once I open the gates a little, it’s only a matter of time before I don’t say no anymore.

Lesson learned.