Have they cracked the secret of a healthy lifestyle?

In the last few days we've had the ideal body weight and the ideal diet. All we are waiting for is the perfect exercise regime - and we probably had that a few months ago. Are researchers really fine-tuning the secrets of healthy living?

This is a personal opinion - that we are actually a long way off. These major global studies give average results. They mix men and women. They may give good guidance - but may also mix individual factors that are critical to my - or your - health.

The Danish diet findings are intriguing. Intuitively they feel right: eat lean protein, whether meat, fish or something vegetarian, because they make you feel full, saturated. Avoid carbohydrates and eat low-sugar vegetables and fruit. It is a healthy version of the Atkins low-carb diet. But the results of the study barely back it up - they show is that this is a good way of keeping your weight down once you've been on a crash diet. And healthy diet is about more than weight, isn't it? It can have a direct impact on risk of heart disease, cancer and other illnesses - possibly.

So what about the distinction between meat and fish. Is that important? Or meat and soy? Or one kind of fat and other?

In some ways the US study of perfect body weight backs the Danes. The researchers say that if you live a healthy lifestyle, then there is a perfect body mass index to aim for. But talk to a health adviser and they may prevaricate. Does this "healthy lifestyle" include being fit or superfit? Body mass may be fat or may be muscle. Doesn't that make a big difference?

We know that weight, diet and fitness all go together. But isn't a little frustrating when sometimes we are told it's the weight you have to get right, sometimes it's the diet and sometimes it's the fitness? Of course the answer is a bit of each - and it's worth paying attention to all these bits and pieces of research. But do we really know why homo sapiens in a large chunk of the world is living for a lot longer than ever before?

Perhaps what we need is a study that tells us whether being a vegetarian bantam-weight body-builder really is the secret of long life and health.