View Full Version : Side effects of low caloric intake

07-15-2013, 05:54 AM
Hi guys,
I've been lifting and watching what I eat for several months now but never really did enough research before I started so treat me as a complete newbie. I now want to learn more about various topics so I can optimise my training and get some good results. I might make some assumptions in my posts that are completely wrong so please tell me if I do. I have written myself a list of questions I want to find some answers to and at the top is this:

When people go on low caloric diets (below maintenance) their BMR eventually adjusts to bring the maintenance calories down to what is being consumed. The same number of calories must be exerted during exercise (if your exercise plan stays the same) so it must be the BMR that is reduced. Wouldn't lowering your BMR be really bad? That suggests to me that your body is skipping processes it would normally do to save on energy. What processes are skipped? Wouldn't this lead to organ failure (dramatic) if the body starts not performing processes it should do? Do you start to always feel lethargic? Does your body temperature drop (thats bad as well isnt it?)?

Lowering your BMR just seems really bad to me but it also seems to be the only way to lose weight...

07-15-2013, 06:16 AM
This is a very good question.

I've always heard that eating at a deficit will slow your metabolism, but I'm not sure HOW it does that. Do organs start shutting down? Is breathing more shallow? Does your heart pump more weakly? Does your body temperature drop? I don't know.

Completely talking out of my ass here, but I suspect that the metabolic slowdown effect is grossly misunderstood. I bet what people perceive as a metabolic slowdown due to reduced calories is actually caused by other factors. For example, reduced carb intake will lower your Leptin levels, which inhibits fat burning. Additionally, eating at a deficit will obviously cause you to lose weight, and as you lose weight, your BMR naturally decreases. Also, eating at a deficit generally causes some fatigue. When you're fatigued, it's natural that your NEAT would decrease as well.

In reality, I don't think eating at a deficit in and of itself slows your metabolism/BMR. In theory, if you operate on a big deficit, but have regular carb re-feeds, maintain your NEAT, etc., I bet your metabolism will keep on trucking as usual - aside from the unavoidable slowdown of your BMR as your weight drops (the larger you are, the more calories you need to operate).

Technically speaking, why would your body start shutting down critical process when it has ample fat there to pull calories from? You may be EATING at a caloric deficit, but your body is still OPERATING at maintenance, in the sense that it's pulling the "missing" calories from your fat. So your body should still be getting the energy it needs, so long as there is fat there to pull it from (and muscles too).

I'm probably grossly oversimplifying here though.

07-15-2013, 06:17 AM
BMR is what your body needs to stay alive if you were in a coma bacically. If it is lowered because you lost weight then that is what your body still needs. You cannot just lower your BMR on purpose, your body lowers it by itself when it knows it can.