After A Diet, Why Does The Weight Come Back?

Before many Australians recently, a devastating story unfolded on a popular current affairs program. We watched with compassion as the fattest man in Australia told of his most recent, serious attempt to lose weight. Approximately 12 months earlier and weighing close to 300 kilos, he under went life threatening surgery to lose weight.
I doubt there would have been one person watching not moved by this man's depression and plight. Despite undergoing the surgery, today he could barely get through each day, both physically and mentally. He shared with us his sense of hopelessness and wanting to end it all.
It was not only his size that was causing his depression. He had to deal with a heart broken by disappointment.
You see, the surgery had been a success.
He soon lost well over 50 kilos post operation and he and his family rejoiced. But then the unthinkable happened.
The weight came back. Today he weighs well over 300 kilos - more than before the surgery.
This is an extreme case, but nonetheless raises a question that so many people continue to battle with.
After a diet, why does the weight come back so quickly?
To answer this we need to understand how much energy a body requires. For each pound you weigh, each day you need 12 calories to maintain your body weight. If you weigh 120 pounds you will need 120 x 12 calories, that is, 1440 calories per day to maintain that body weight. If you eat or drink more calories than your body requires, the excess energy is stored as fat. It takes 3,600 excess calories to make one pound of fat.
In this example, if your typical daily calorific intake is 2000 calories, in around 30 days you would put on between 4-5 pounds of fat!
Let's say, you then decide to go on a restrictive diet and halve your calorific consumption to 1,000 calories per day. You stay on this diet for around a month and lose 10 pounds and now weigh 110 pounds. You feel fantastic about losing the weight but can't keep up such a restrictive regime because you are irritable and have no energy.
So you go off your diet and go back to your usual routine of 2,000 calories a day. Remember you are lighter now and your body requires less energy to maintain its new weight. You would now require 110 x 12, that is, 1320 calories per day.
In this instance, by consuming 2000 calories daily, because you are lighter than before, you would put the weight back on in just 24-25 days!
If you want to keep the weight off you must develop a consistent change in eating habits to ensure you do not consume more than your body requires. You cannot continue to eat the same quantities and/or combinations of foods that caused you to be overweight in the first place. This will require developing an understanding of the nutritional content of food and raising your body's metabolism through increased muscle mass and exercise.
(c) 2003 Kim Beardsmore