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Insulin and Kcal-Surplus/Deficit



As far as I know insulin is said to be an "anabolic hormone" which means that it tells your body to start building mass (muscle and fat). But it is also said that whether you gain weight or lose weight is ONLY determined by your calories IN/OUT-balance.

I just can't really understand how these two things work. Why is insulin important for a postworkoutshake but creating a kcal surplus isn't? How can insulin tell the body "start building" when you don't supply enough calories?

I hope somebody understood what I'm asking :slightly_smiling:


So you're asking about nutrient partitioning. Even when we eat only at maintenance we are technically rebuilding all the time. Working out signals the body to prioritize rebuilding muscle, and providing nutrients at that time as opposed to any other optimizes that window.

So you can be on maintenance and get leaner and more muscular all be it at a slower rate and to a limited degree (because your metabolic rate may increase along with LBM, at which point you really do have to consume more to continue).


what has been "said" aint exactly true. My suggestion is to do a little more reading. Your questions arent 100% clear but maybe its because Ive been up for a while. Insulin is also a fat storage hormone. It depends on the goal (regarding post wod food/shake). Whats your goal? Over all cals dont build, specific macros do. 3000cal of lettuce and 1 post wod shake aint gona build the guns, or at least I havent seen that happen yet.


I don't understand why you're confused. One is the WHAT and the other is the HOW.

I also don't understand why you're thinking about caloric surplus (in the scope of this discussion, a chronic condition) in the terms of a post workout meal (in the scope of this discussion, an acute condition).


My goal mainly is to build muscle. Ofc 3000kcal of lettuce won't help me but if I need only 2800kcal for maintainance it will cause my body to at least store fat/gain weight or not?

Yes maybe that is whats confusing me. A caloric surplus is usually talked about as a condition which lasts quite long but insulinsecretion is something that happens in one particular moment. The thing is that as far as I know BOTH things help(probably an understatement) to build muscle (if your training is solid of course).

If you just worked out your probably in a kcal-deficit if you don't eat. Now you can set up your postworkoutmeal/shake in various different ways. You can eat lots of calories (from protein and maybe fat) or less calories. And you can either consume lots of high/medium glycemic carbs or not. So after your meal there are 4 things that can happen:
1. kcal surplus and high insulin
2. kcal surplus and low insulin
3. kcal deficit and high insulin
4. kcal deficit and low insulin

Number 1 is probably the one thats most "anabolic" and number 4 is probably useless.
But what about 2 and 3?
Most people advocate to get your insulin high in a postworkout meal. But how can that make you build any muscle if your still in a kcal deficit?
And if your in a kcal surplus your having and excess of energy(kcal) that will be stored, how can it matter that your insulin is low at that time?


I'm not quite sure exactly what you mean in 1-4. The kcal surplus or deficit you are referring to is overall/long term right? Otherwise I don't understand how you quantify surplus or deficit (fasting/non-fasting?)

Perhaps it is important for you to remember that the body does not work in 24 hour periods. Your body (or tissues) can be in an anabolic state for several hours. Following that, it does not necessarily mean that you will be in a catabolic state if you are in an energy deficit. The issue gets more complex when we consider all the different tissues in the body. Some tissues can still have a high anabolic/catabolic ratio when in a caloric deficit while others will have the opposite.

Insulin and excess energy can promote muscle growth by different and over lapping mechanisms. So there should be some additive effects. Also remember that these mechanisms are not all on/off states.


@OzyNut well if thats the case and everything is that complex then it is probably absolutly useless to continue to think about this stuff :smiley:
But no, I don't mean that the surplus is longterm. I just mean that in the particular time of the postworkout meal (lets say 2 hours after training) the body has excess calories. Maybe you burned 350 kcal in your workout and you need 150 kcal in that time to maintain your bodyweight (thats called BMR I think). If you now consume 501 or more kcals in THAT particular meal you should be in a surplus at THAT particular time. Hope you understood what I mean..


Let's see if we can make this simpler.

So I sit on my ass all day and eat above maintenance. My excess nutrients, depending on the composition and my level of genetic giftedness will be deposited as glycogen first then fat and muscle (muscle to a lesser degree).

If I'm not working out I'm not really affecting my muscle glycogen and my liver glycogen will probably be in the normal range if I consume adequate carbs. So this means I'll mostly be replenishing and slowly increasing my fat stores. Keep in mind, what little energy I am consuming is coming from the carbs, then liver glycogen and fat stores which is why they must be replenished, and as I gain weight I will gain a small quantity of muscle even with little exercise (according to that overfeeding twin study I read about long time ago).

Case 2. I eat in surplus throughout the day. I workout once and I consume most of my carbs in the post workout window. I will deplete glycogen with my workout, so that will be refilled first, I'll also increase my body's rate of protein synthesis and insulin will help the carbs and protein I have consumed be used for that purpose, creating a bias toward building muscle for a duration. Keep in mind that earlier in the day, if consuming carbs and relatively innactive that is where I will derive most of my energy.

Case 3. I eat in a deficit when considering the day as a whole. If underconsuming carbs earlier in the day I will derive my energy from what carbs I get, liver glycogen, then probably fat (if everything else is normal) and also a little bit from protein. I workout and employ common peri-workout nutrition putting most of my carbs around that time. At this point I rebuild my muscle to a degree (what level will be determined by the nature of my workout and the quality of my peri-workout nutrition).

In that case it may be possible to maintain or slightly increase muscle mass (wouldn't be very dramatic) while preferentially losing fat throughout the day.

Case 4. I'm at maintenance but again I watch my peri-workout window. I can gain muscle and lose fat (not as dramatically as cutting and bulking) and there will be a limit to how much muscle you can gain from doing recomposition because your metabolic rate will slowly increase if your recomposition is successfull. So you're essentially shuffling things around. No breaking the laws of thermodynamics here.

Intermittent fasting proposes to create a 16 hour defecit for fat loss through the day. And a surplus around the time of your workout to make this effect more dramatic.

Carb cycling proposes to create deficits on rest days where the carbs and accompanying insulin would not especially favor muscle.

Nobody as far as I'm aware recommends momentary underfeeding after a workout. So I won't even describe that scenario, cause you can see how it's bad.

I may be incorrect on some of the details here but the general idea is consistent with findings.


@timboo Yes you have a point. Technically, after any meal a person will be in a caloric surplus for a duration of time. So, how does the degree of caloric surplus per meal affect potential muscle growth? I don't know.
Compare repeated (6 meals per day) to one massive meal - one situation you are repeatably hitting caloric surplus and the other just once (but with one hell of a hit). Which one is physiologically better?
In the short term we can only extrapolate from muscle biopsy and animal studies - which are likely not designed to look specifically at what we want to know.

So, its best to only consider caloric surplus/deficit over predefined time periods - the longer the better.

However, the insulin signaling cascade and physiological implications are quite well defined. So we know that insulin can stimulate protein synthesis in muscles.

So overall, not having either isn't a make or break deal. Both can be used together additively.