Pursuits: Weighed in weight theories

Is there anything more annoying than a doctor who tells you that you are too fat because you eat too much and don’t do enough exercise?

For years and years, doctors stuck to the simple calorie-counting line. Your body is a machine, they said. You put in fuel and either you use it or live with the consequences when it is stored as fat.

 

When patients tried to explain that they did not actually eat very much, doctors would dismiss it. “You just don’t realise how much you are eating!” they said. “Keep a food diary. Make a note of everything you eat. And then you’ll see how much you are really eating!”

 

   The problem for the doctors is that people actually started keeping such diaries. And soon, scientific studies demonstrated that the human body is not really a fuel-guzzling machine. If two people both eat an identical diet and perform identical levels of exercise over a specific period — say, one month — then they should put on identical amounts of weight. In fact, as scientists have demonstrated, this does not happen. The amount you eat and the amount you exercise does have a relationship with weight loss but it is not a simple and direct connection. Some people gain weight more quickly regardless of what they eat. And some people don’t put on weight no matter how many cheeseburgers they consume.

 

   Faced with these scientific test results, doctors changed their story. Now it was all about metabolism. Apparently, some of us burn up calories faster than others. To stick with the machine analogy, thin people are like fuel-guzzling motorcars. They need lots of fuel to keep going. Fat people have a better petrol-to-mileage ratio. They need very little food or fuel. And when they eat as much as a normal person should, the unused fuel is stored as fat. So, we are like machines. Except that when it comes to the human body, it is better to be a gas-guzzler.

 

   A whole diet industry has grown up around the metabolism-is-the-secret theory. Dieticians tell us that, yes, the simple calorie-counting approach does not work. If you jog around the block a couple of times and think that you have expended lots of calories, well then, think again. You’ll come home and eat a piece of toast with butter and jam and discover that it contains twice the calories that you have expended on your jog.

 

   Some nutritionists claim that exercise has the effect of raising your metabolic rate so if your body is constantly on the move, it will burn up calories faster. Scientists concede that there is some basis to the claim, but reckon that it is routinely overstated by dieticians. You can’t keep having large meals and believe that it is all going to be okay if you go for a jog every morning. And as for walking, now regularly recommended by doctors and dieticians, take a look around the park the next time you go walking. Nearly everybody else you see will still have a paunch even though they will claim to have been walking for years.

 

   The metabolism-is-the-key lobby now has a new solution. If you eat something every two hours, this will keep your metabolism high. So, the trick to losing weight is to have six small meals a day. Well, it works for some people. But generally speaking, the secret is that the small meals they allow you to have are so tiny (a handful of nuts) that you end up eating much less than you would normally. And for many people, this method doesn’t work at all.

 

"As research into bacteria increases — and bacteria have replaced genes as the favourite subject of scientists — dieticians and nutritionists are certain to seize on the subject."

   Another school of dieticians believes that carbohydrate consumption is the most important factor. The current epidemic of obesity in America, we are told, has its roots in the popularity of carbohydrate-heavy junk food. Cut out carbohydrates and you will lose weight. This sounds counter-intuitive to people brought up on the calorie-counting approach because meat has more calories than, say, a bowl of rice. But there is no doubt that it works. However, it is no more than a short-term solution because your body needs carbs and you will eventually get carbohydrate cravings. And research shows that once people on low-carb regimes return to their normal diets, the weight returns as well.

 

   There’s now a new approach to weight control. Scientists are fascinated by gut bacteria. All of us carry millions of bacteria in our bodies. Each of us is inhabited by as many as 10,000 species of bacteria. At a conservative measure, we have ten times as many bacteria as we have cells in our body. If we were to put all the bacteria in our body together, they would weight around 3 pounds per human being.

 

   And yet, science has shown little interest in them. The classic example is that of H.pylori. For decades, doctors told us that ulcers were caused by stress. Then, in 1982, two scientists discovered that H.pylori was the primary cause of gastritis and peptic ulcers. The idea that ulcers were caused by an infection and not by stress was revolutionary but it took doctors at least ten years to start prescribing the right kind of medication to kill the bacteria.

 

   Scientists now have a better idea of the damage that bacteria can do to our systems. But they still don’t understand the positive effects of bacteria within the system — and there are many. Nor do they understand that even so-called bad bacteria can sometimes be good for you.

 

   Take H.pylori, for example. We now know that H.pylori helps protect our systems against asthma. When we discuss how asthma rates have gone up all around the world over the last few decades, we usually blame it on pollution. But, scientists have demonstrated that as more and more of us take antibiotics, we kill the H.pylori in our system, which is the body’s natural defence against asthma.

 

   Now, scientists have found a link between H.pylori and obesity. Our appetites are controlled by hormones. Two of these hormones are leptin and ghrelin, which tell us when we are hungry and when we are full. It turns out that H.pylori controls the secretion of ghrelin. People with H.pylori in their systems release less ghrelin. Those without H.pylori keep releasing ghrelin and therefore, tend to overeat.

 

   Research into the links between bacteria and the human body is still in its infancy. All that medicine is sure of is that some bacteria cause disease and so, they must be killed off with antibiotics. What doctors don’t realise is that bacteria perform a more complex function in our bodies. When you kill off all bacteria, you kill the good with the bad. And perhaps, there is no such thing as the division between good or bad anyway. In one context, H.pylori can cause ulcers. In another, it can protect against asthma and overeating.

 

   As research into bacteria increases — and bacteria have replaced genes as the favourite subject of scientists — dieticians and nutritionists are certain to seize on the subject. Many American scientists believe that their country’s obesity epidemic is not caused by McDonalds but by bacteria. So, the next big thing in the diet world will not be exercise, metabolic rates and no carbs. It will be bacteria.