First lets talk about who needs to lose weight and why. Weight of course varies with height but what we are really interested in is what percentage of your body is fat. This is not quite as straightforward as it sounds. The only accurate way to measure per cent body fat is to weigh you and then dunk you in a tank of water to see how much water you displace. This is obviously not a practical way follow your fat percentage, so we use several methods to approximate the percentage of body fat.
The most common (and easiest) method to estimate body fat percentage is called body mass index or BMI and is measured in kilograms per square meter. This method works fairly well for most people, but it overestimates body fat percentage for some people, especially men, with large amounts of muscle mass. Normal BMI is between 18 and 25. Here is a calculator to compute your own BMI.
Another way to estimate the percentage of body fat is to use special calipers to measure the thickness of skin folds on standardized places on your body. This can be very accurate, but takes a lot of practice to do correctly, so is not very practical for most people to use. Body fat percentage should be less than 20% for men and less than 30% for women.
The third method is called bioelectrical impedance. A tiny electric current is passed through your body and the resistance to current flow is measured. Because water passes more current than fat, higher resistance means more fat. This is probably the least accurate measure because it is also affected by your state of hydration, but followed over time it can be useful. The most common consumer device that uses this method is the Tanita scale. There are several models to choose from depending on your budget.
If your BMI is less than 40 or your percent body fat is 40% or less for women and 30% or less for men, all you need to do is follow the seven secrets to a long and happy life and not worry about your weight. If you are beyond those limits, then your weight may be detrimental to your health and it makes sense to try to lose weight.
If you do have a weight problem, no doubt you have read many diet books and tried just as many diets. The good news is that almost all of them work as advertised. The bad news is that within a year, usually less, all the weight comes back and more. Why does this happen?
It turns out that recent research has an answer. When you have been at a certain weight for a long time (we don’t know exactly how long that is) your body takes that weight as a set point and just like a thermostat, your body tries to keep you at that weight.
When you go on a diet and lose weight, your body goes into action to try to get you back up to your set point weight. For one thing, your muscles get more efficient so that you burn fewer calories with the same amount of exercise. Also, there is a hormone called leptin that lets you know when you have had enough to eat at a meal. When you lose weight, leptin levels go down so that it takes larger amounts of food for you to feel full. There are other complex changes in your body chemistry, all designed to get you back up to your set point weight.
So low long do you have to stay at a lower weight to have it as a new set point? We don’t know for sure, but at least a year and perhaps longer.
Pretty depressing, isn’t it?
The only way to beat this system is to make permanent changes in your eating and exercise habits. That rules out all the diet books, because none of those diets are sustainable for the rest of your life. In order to make permanent changes you have to choose carefully. You are more likely to stick to small changes than big ones.
For example if you happen to love ice cream you are probably not going to stick to a change of no more ice cream ever. Maybe you could permanently manage having ice cream only once a week, however. One way to decide what to change is to keep an eating diary for a week and then use the diary to decide one change you think you could live with forever. Once you are successful with that you can keep the eating diary for another week and decide on another small change.
Sometimes very simple things can work. For example one way to automatically reduce portion sizes is to eat off a salad plate rather than a dinner plate. Research has shown this has a subconscious psychological effect. A smaller amount of food looks like more on a small plate. This and other findings about how the presentation of food affects the amount we eat is described in an excellent book by Brian Wasink called Mindless Eating.
What about exercise? You are not likely to lose weight through exercise alone without making changes in your eating habits unless you are doing vigorous exercise for hours a day. That’s just not practical for most folks. Moderate exercise is good for you in other ways though and makes you feel better, which indirectly may help you change your eating habits.
Eventually as you make small permanent changes In your eating and exercise habits you will start to lose weight. It won’t be fast but it’s likely to stay off, and it’s the only way to beat the thermostat system. A realistic weight loss goal is 10% of your body weight over 6 months to one year. If you achieve that and sustain it, then you can set a goal for another 10%.
In my experience there are a few people who follow all these rules and still do not lose weight. Although that is discouraging, following the seven secrets to a long and happy life will still serve to improve your wellbeing and decrease your risk of health problems related to your weight.