I don't know if we are still at the head of the substance abuse league (we always knew there were some things we could do better than anyone else), but obesity has now become sufficiently disturbing for it to become a focus of Government policy, which means that it has to be seriously bad.

It seems that no sooner are we coming to terms with Scotland being at the head of the European league of substance abuse, than we discover that we're also prone to another more subtly addictive substance - food.

Dr. Philip James (director of the Rowett Research Institute in Aberdeen) has been in Mexico this weekend chairing the International Task Force on Obesity, which suggests that one in six British adults are clinically obese. Even our children are overweight, and in Scotland our boys are getting fatter faster than most, rapidly heading towards claiming the title of the fattest kids in Europe.

This self-indulgence isn't good for us. Not only is it hugely costly to society (about a million pounds a day in the NHS alone), but it also has a traumatic effect on individuals, locked in a vicious circle of negative self-imagery, low self-esteem and comfort eating. It's that old trick of the Devil, persuading us that happiness lies in self-gratification, whereas in fact the opposite is true. Our happiness and well-being as individuals and society actually lie in self-discipline and self-restraint.

Muhammad was known as the most laughing and smiling of men, but his happiness certainly didn't come from self-gratification. Though ruling Arabia and having access to all the riches that passed along its trade routes, the Prophet's diet was always simple and minimal, mainly coarse barley bread, a few dates, and occasionally a little meat.

His generosity was such, that his wife said he frequently gave away all the food they had to the destitute. It was said that he never ate three days in a row, and he was sometimes known to strap a stone to his stomach to assuage the hunger pangs. He told his companions "No man fills a vessel less worthy of filling than his stomach. Sufficient for the son of Adam are a few mouthfuls to keep his back straight, but if it has to be more then let one third of his stomach be for food, a third for drink and a third for breathing". "He is not a believer who eats his fill while his neighbour remains hungry by his side."