Caloric Restriction or Carb Restriction... which causes a metabolic slowdown?

Answered on August 19, 2014
Created February 04, 2013 at 6:07 AM

Ok guys,

I tend to hear a lot of things about the place, and wanted an opinion in a forum. And perhaps even a few studies if you know of them.

What exactly causes metabolic slowdown? I've read that it is through caloric restriction, and that your metabolism becomes more efficient, which makes a lot of sense. But when I hear that it can be caused by the restriction of carbohydrates, I start to wonder, Why???

I know that caloric restriction can affect Leptin levels as well, and on the likes of a CKD, the weekly refeed is used to refill glycogen and regulate your leptin levels... or is that because of the overfeeding itself?

Eh, as I said, its more to understand my own body and to also discuss with my fitness friends as to what really causes this kind of metabolic issue... as I've been suffering it myself, and decided to go on a break from everything diet wise, for psychological as well as physiological purposes, as I believe my metabolism has slowed down considerably and am trying to bring it back into balance over the next 3 weeks.

Ok... GO!

~ Cricket



on February 04, 2013
at 08:38 AM

Cheers for the n=1. Personal experiences really do give me an idea :)

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5 Answers



on February 04, 2013
at 08:15 AM

I was having trouble losing weight with low carb so I kept cutting more and more calories but nothing budged it. At the same time my TSH was almost 6. I couldn't get more refined thyroid tests so I asked for an endo referral which took about 3 months.

Meanwhile I tracked my calories to see if I could cut even further. I thought I was at about 1200, but it turned out most days I was under 1000! So I bumped up my calories to 1200 -1300 and started to lose again. Not only that, but by the time I saw the eno my TSH was 3.5, coming down nicely. The endo denied diet could have anything to do with it("just a normal fluctuation") but I'm sure if I'd already been on T4 hormone she would have attributed it to that.

Bottom line is the carbs were the same throughout. In my case I have no doubt that calories, NOT carbs, were the culprit.



on February 04, 2013
at 08:38 AM

Cheers for the n=1. Personal experiences really do give me an idea :)



on February 04, 2013
at 01:54 PM

My own personal experience has been that cutting carbs has only helped me lose weight whereas the amount of calories I've consumed has increased. From this n=1 thinking I would say that it's calorie intake which causes a metabolic slowdown. I would guess that's also the reason why I feel more tired after days where I've consumed a smaller amount of calories whereas my energy levels are, more or less, unaffected by the amount of carbs I eat (which is in the range of 15-35g/day).

I know this is very anecdotal (and not scientific), but I just wanted to give my 2 cents.



on February 04, 2013
at 06:41 AM

Yeah, losing weight typically decreases energy expenditure. Whether this is due to some effect of leptin I don't know. I'm guessing probably.

Either way, it's probably not carb restriction bringing about this "metabolic slowdown", otherwise greater carb restricting diets would bring about a greater decrease in resting energy expenditure, but they don't:




I'm betting that it's largely the loss of metabolically active tissue (fat and possibly muscle) that causes this dieting induced decrease in caloric expenditure.



on February 04, 2013
at 06:34 AM

The metabolism during carb restriction and calorie restriction is very similar.

This is one angle....


I'll expand my answer tomorrow with a full sleep ;)


on February 04, 2013
at 06:24 AM

I was actually just watching Fat Head earlier and it explained this. Here is the link:


The part about carbohydrates and calories starts at 1:24:11

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