When I was a child, my mother thought my brother was not going to live because he was so painfully thin. He did not eat much, and she pushed as many calories into him as possible.

Gradually over the years, his weight became acceptable, and by the time he was in his 30s, he was pleasantly plump, gradually increasing in weight with each passing year.

There is no question that something happens to our metabolism when we become young adults. This alteration (not well understood, I might add) leads to the beginning of weight gain that averages about a pound per year until about age 65 and then levels off. Weight gain becomes less common after age 75.

In the past 50 years, being overweight has become the norm rather than the exception, and children are becoming ever more obese. We have blamed this change on a sedentary lifestyle, unhealthy food choices, large portion sizes and the consumption of far too many calories.

In the mid- and late-20th century, fat and cholesterol took the blame. A low-fat diet became everyone's goal. Fat intake was restricted, but starch and sugar were not, and sadly we became even more rotund. Recently, a great deal of evidence is accumulating that refined sugars, such as table sugar or sucrose and high fructose corn syrup, are a major cause of weight gain. Many decried sugar's negative effects on health, including an increased risk of heart disease, diabetes, weight gain and, of course, dental issues.

Even though this was well accepted by some, the research evidence left much to be desired, and many experts in the field felt that the cause was not how much sugar one consumed but how many calories.

In a new study published in the prestigious journal BMJ, researchers demonstrated a very significant correlation between increased sugar intake and weight gain. And — vice versa — reducing sugar intake led to weight loss.

The link between sugar intake and weight was very strong in adults but less so in children, presumably because their diet is so varied. However, if you looked only at sugary drinks consumed, the more sugar taken in by children, the fatter they were.

The World Health Organization recommends that refined sugar should constitute less than 10 percent of total calories consumed. According to the U.S. Department of Agriculture's Center for Nutrition Policy and Promotion, sugar intake in Americans ranges from 16 percent to 20 percent of total calories consumed. And when the fat content of the diet is restricted, excess carbohydrates from starches, cookies and other fat-free products are used to assure a calorie intake that causes satiety.

Too much sugar and starch in the diet leads to weight gain and the so-called "metabolic syndrome." In the body, refined sugars and carbohydrates are converted to glucose. To maintain a normal blood sugar, excessive amounts of insulin are released from the pancreas, and the glucose is pumped into cells where the excess is converted into a special form of fat called triglycerides. These enter the bloodstream and are stored in fat cells.

As weight is gained, insulin loses its ability to reduce blood sugar to normal. This is referred to as insulin resistance, and it leads to Type 2 diabetes. These individuals are overweight, have very high triglyceride blood levels and are prone to cholesterol deposits in blood vessels and heart disease, stroke, high blood pressure and kidney disease. The most remarkable aspect of this "self-made" disease is that it is eminently curable by diet and exercise.

Anyone who has developed the metabolic syndrome and insulin resistance and is overweight should see a diabetic educator. An appropriate diet and an exercise regimen frequently return the blood sugar to normal, reduce the risk of heart disease and prevent hypertension.

The fact that sugar and, to a lesser extent, too much starch, have negative impacts on our weight provides more compelling evidence that the best diet is prudent, contains the right amounts of fat, fruits and vegetables, protein and sugar and starch in moderation. Combined with exercise and a healthy outlook on life, serious illness can be prevented and a longer life assured.

Dr. David Lipschitz is the author of the book "Breaking the Rules of Aging." To find out more about Dr. David Lipschitz visit www.drdavidhealth.com.