Starvation Response: Why drastic calorie reduction does not work

When trying to throw some light on the quintessential question “Why do we crave sugar?“, I mentioned how well the human body has adapted to changing situations. The eternal hunt for sweetness, however, is only one of the amazing things we have learnt over years of living in different environments. Famine, drought, predators, nature and peer-competition, each has played an influential role in shaping human beings into the unique position we are in today, right on top of Nature’s food chain.

When man still had to hunt for his next meal, there were often times when he had to go days without food and the starvation response most likely developed as a natural response to reduced availability of food. If we had to define, it …

Starvation Response

Starvation response can be defined as a proportional reduction in metabolism in response to reduced availability of food. While the physiological (and even psychological!) response is obviously way more complicated than that and differs among different people, the general response is still similar: when faced with a sudden drastic shortage of food, the human body reacts as it has always been trained to by evolution: it reduces its metabolism (or the rate at which it uses calories for energy) by slowing down physiological processes. This can be understood as just a normal reaction to conserve resources.

When you’re faced with a situation where food is limited, your body senses this and tells itself - “Hey, we better stop burning all these calories so quickly because it looks like we’re having a shortage of calories lately, and this may go on for some time. Let’s slow down and start saving more energy so that we can survive longer under these conditions with the little food we’re getting”.

- The Daily Muscle

Why drastic calorie reduction does not work

Well it works in the sense that it does what it is supposed to do: slow down your metabolism, but it does not work in the sense that it won’t help you in your long-term weight management/control goals. Consider:

Say your daily basic caloric requirement is 2500 calories (this is required just to keep your body functioning) and you consume 3500 calories a day with no added expenditure (exercise or labor-intensive work). It doesn’t take a rocket scientist to tell you what’s going to happen to 1000 excess calories you have no use for.

Then someone tells you about this informative blog that tells you the whole truth about calories (hint! hint!!) and you decide to reduce your calorie intake to below maintenance levels so that the excess can be made up from body reserves. But you take it too far: Say you reduce 1000 calories or more and eat just 1200-1400 calories a day. In three and a half days you have cut off 3500 calories which is one pound of fat - at this rate you should lose about 8 pounds a month - but that never happens for extended periods.

Initially you might see a noticeable loss of weight but soon, your body’s starvation response kicks in slowing down your metabolism. This means you no longer need 2500 calories any more - so your supposed reduction of calories is not as great as you once thought and this leads to reduced reduction in weight over time.

Disadvantages of drastic calorie reduction

As already discussed, your metabolism slows down as a result of starving yourself - but there are other implications as well:

1. When you reduce calories this drastically, you will also lose valuable muscle weight (you don’t really lose the muscle itself - it just becomes smaller!). This makes sense for the body too because muscles are not easy to maintain and cost the body more calories to maintain than fat. Losing muscle weight is thus a double whammy: you are not only losing something that is valuable and difficult to grow but you are losing something that would have been a valuable ally in helping you lose what you really want to lose: fat (if that was too confusing, just know this: A. muscles are difficult to grow. B. muscles increase your metabolism and help you lose fat)
2. Say you achieve some sort of “success” (in quotes because you may have reduced weight, but not all of it is likely to be fat) and have reached some acceptable weight. Almost 95% of the people will then go back to their old way of eating, but guess what: with a reduced metabolism (thanks to our friend, starvation response and the possible consequence of muscle-weight reduction), they are prime candidates for the rebound effect: gaining back the weight they lost and then some.

The bottomline

While reducing calories to a little below maintenance levels will help in keeping your weight under control and begin the process of reducing the fat stores in your body, drastic reduction will have the adverse effect of slowing down your metabolism and reducing muscle mass.

In general, reducing more than 500 calories at a time below your current maintenance level is not advisable. Infact, even the calorie calculator I recommended earlier gives you similar advice (compare the total calories between “Lose Weight” and “Maintain Weight” scenarios for your weight and height).

So there you have it: Stop starving excessively in an effort to lose weight. Mild calorie restriction coupled with an active lifestyle and exercise is the sure-fire way to stoke your metabolism, maintain (even increase) your muscle mass and lose weight in the long run.

Only then will fitness truly be your way of life.

[tags]health, fitness, nutrition, starvation response, weight loss, fat loss[/tags]