There are many reasons why being overweight is bad for your health. It can, for example, cause or aggravate type 2 diabetes. Obesity is also a risk factor for heart disease and other cardiovascular problems.
So what do you have to do to lose weight?
Eat less and move more is the trite answer usually received by someone who is overweight.
Of course you can lose weight by reducing the food you eat (energy intake) or increasing the amount of exercise you get (energy output).
But the problem of effective weight-loss is much more complex than simply changing the balance between the calories you consume and the calories you expend in your daily activities.
The search for an effective weight-loss formula requires answers to these four questions:
Does genetics play a role in your weight problems and, if so, what can you do about it?
How many calories do you need to cut from your diet to lose one pound or kilogram?
What are the best types of foods (carbs, fats or proteins) to cut for losing weight?
Is exercise much good in helping you lose weight or for keeping weight off?
How genes affect your weight
Many people do their utmost to lose weight without much success. In particular, once they have lost a few kilos, they find it extremely difficult to keep their weight down... it just rises back up again.
This suggests that the problem is genetic.
In fact, more than 30 genes have been linked to obesity. The one with the strongest link is the fat mass and obesity associated gene (FTO).
The obesity-risk variant of the FTO gene affects one in six of the population. Studies suggest that persons who have this gene are 70% more likely to become obese.
According to research published in the UK in 2013 in the Journal of Clinical Investigation, people with this gene have higher levels of the ghrelin, the hunger hormone, in their blood. This means they start to feel hungry again soon after eating a meal.
In addition, real-time brain imaging shows that the FTO gene variation changes the way the brain responds to ghrelin and images of food in the regions of the brain linked to the control of eating and reward.
These findings explain why people with the obesity-risk variant of the FTO gene eat more and prefer higher calorie foods... even before they become overweight... compared with those with the low-risk version of the gene.
The FTO gene is not the only genetic cause of obesity, which is likely to be due to the sum of several genes working together.
If you have these 'bad' genes, however, you are not necessarily destined to become overweight... but you are more likely to end up obese if you over-eat.
Having these genes also means that you will need to exercise greater discipline over your diet throughout out your life, especially when you have managed to shred a few pounds and want to keep them off.
How many calories should you cut to lose weight?
The big question for dieters has always been... how many calories do I need to cut out of my diet in order to reduce my weight by a set amount, eg one pound or kilogram?
Once upon a time there was a clear-cut answer to this question.
In 1958 Max Wishnofsky, a New York doctor, wrote a paper that summed up everything known at that time about how calories are stored in our bodies. He concluded that, if your weight is being held steady, it would take a deficit of 3,500 calories to lose one pound (454 grams) in weight.
You could create the calorie deficit either by eating less or exercising more (to use up more calories).
For example, if your weight is holding steady on a diet of 2,000 calories a day and you reduce your intake to 1,500 calories a day, you will lose one pound (nearly half a kilo) in one week, ie 52 pounds or 24kg a year.
Alternatively you could burn an extra 500 calories a day (through exercise) to lose the same amounts of weight over the same time periods.
For years, the Wishnofsky rule was accepted as a verified fact. It underpinned a wide variety of diets.
The only problem is that the rule is wrong. It fails to take into account the changes in metabolism that take place when you go on a weight-reducing diet.
The Wishnofsky rule actually works initially. But after a week or two your weight reaches its minimal level, much to the frustration of myriads of dieters, as your metabolism adjusts to the decrease in your body mass and your reduced intake of food.
Until recently there was no way to predict how consuming fewer calories affects the rate at which you will lose weight, especially when your goal is to lose more than just a few pounds or kilograms.
There are now, however, new complex weight-loss formulas that factor in the drop in metabolic rate that occurs over time as body mass decreases. One example is the Body Weight Planner from the National Institute of Diabetes and Kidney and Digestive Diseases in the USA.
What types of foods should you cut to lose weight?
What types of foods should you cut to lose weight?
Should you reduce your calories from your fat, carbohydrate or protein intakes? Which will help you lose weight faster?
The numbers of calories in one gram of each of the basic food types are as follows:
Fat... 9 calories per gram
Drinking Alcohol... 7 calories per gram
Proteins... 4 calories per gram
Carbohydrates... 4 calories per gram
Dietary Fibre... 2 calories per gram
As fats contain more than twice as many calories as carbs and proteins, reducing the fats you eat will work twice as quickly as a reduction in either of the other two types of foods, gram for gram.
This is why diets that concentrate on reducing the fat you eat, such as the Beating Diabetes Diet and the Mediterranean Diet are effective in reducing weight.
But if you want to cut your calorie intake by a fixed amount a day (say 500 calories) will it make any difference as to which type of food you cut down on?
For example, will it make any difference to the amount of weight you lose if you cut 55.6 grams of fat (500 calories) or 125g of carbs (500 calories) or 125g of protein (500 calories) from your diet?
The answer is that there is little difference in the amount of weight people lose whether they cut their calories from carbs or fat.
But calories from proteins are different... according to researchers, high-protein diets tend to increase the number of calories you burn. Why this is so is not clear.
However, when people lose weight they lose muscle as well as fat. The more muscle you lose the more your metabolism slows down which reduces the rate at which you lose weight.
Because it preserves muscle, a protein based diet may reduce the rate at which your metabolism slows down.
The problem is that, if you eat too much protein, you could end up damaging your kidneys. The generally accepted recommendation is that you limit your protein intake to a maximum of 35% of your total daily intake of calories.
So, provided you don't eat too much protein, it is best to reduce weight by cutting down on fats (for the sake of your heart etc) and refined carbs that spike blood glucose levels (especially if you have diabetes).
Does exercise help you lose weight or keep it off?
Cutting down on the food you eat is the best way to lose weight. Exercise is less important, at least in the initial stages.
Exercising when you are trying to lose weight can be tricky. It burns calories for sure but not nearly as many as not eating those calories in the first place.
And exercise increases your appetite, so it is easy to eat back on all the calories you burn during an intense work out.
The recommendation, when you are cutting your food intake to lose weight, is to focus on moderate physical activities such as gardening or brisk walking, rather than going to the gym.
But once you have shred those extra pounds and are down to your ideal weight, exercise becomes important for maintaining your weight at its new healthier level.
Researchers have found that most people who lose weight and manage to keep it off for at least a year exercise regularly for up to an hour every day.
By Paul D Kennedy
