BG2: Myth busting

About 6 day ago I regurgitated the concept of “starvation mode”.  Reader and BG2-er Wayne was quick to tell me that I didn’t know what I was talking about, and went on to explain.  You may have missed it, so here it is again.

As for starvation mode, the basic concept is that if you fast or skip a meal, or reduce your calorie intake even slightly (you’ll find many variations) then your body enters “starvation mode” where is is more efficient. Therefore skipping meals, fasting etc is useless/counter-productive/will make you gain weight.

This is completely false.

The idea based on a tiny kernel of truth from one very old study. To summarise, if you are truly starving (say about 10 days without food), then your basal metabolic rate will drop slightly as your body enters this “starvation mode”. For most people this was a drop of about 3-6%. The most extreme drop was 10%.

Now your basal metabolic rate is how many calories you would burn if you lay in bed without moving – no finger twitching – nothing voluntary. You can estimate this at about 1200 calories per day. So at the most extreme, if you entered starvation mode by not eating at all, you might eventually burn 120 calories less per day than you otherwise would. Realising that you have to not consume over 2000 of calories to reach this state. So you will still be losing weight.

In short, “starvation mode” as it is popularly presented

a) will never happen, because you are not, in fact, starving
b) is only a tiny effect
c) does not in fact negate the effect of fasting, skipping meals, or actual starving
d) only affects the basal metabolic rate

Furthermore all forms of exercise, jogging, cycling, swimming, walking to the fridge, digesting food, all burn the same number of calories whether you are in survival mode or not. And unless you are in a coma, these calories burned from moving around are far in excess from any “starvation mode” savings. And remember this saving for most literally starving people is a saving of less than 8g of fat per day.

One thing to realise is that your body is breaking down (“eating”) both muscle and fat all the time, even when you are eating. There’s a dynamic equilibrium as old cells die and new cells are formed. If you aren’t loading your muscles (“keeping fit”) then there is less demand to create new muscle cells, and so there is a net loss. If you are consuming more calories than you burn/excrete then there is a net gain of fat cells. But the two are being create and consumed all the time. The net effect is the concern.

A side issue is that a fat cell can be fat (stuffed with fat) or skinny, and once a fat cell is made it is easier for it to store more fat. But the above paragraph is still true.

– Wayne

Thanks for that Wayne, good stuff.

I’ve certainly found that on my “normal” days, I am probably eating a little less than my basal metabolic rate, which is why the weight loss tends to continue.   Once you do fasting days where you eat only 600 cals over a day, then 1500-2000 cals a day is a feast, even if your basal rate is more than that.

I did have two chocolates yesterday.  Yum.  snigger


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