My name’s Russell Viner. I’m a consultant in Young People’s Health Adolescent Medicine and Endocrinology, and work at University College Hospital, and Great Ormond Street Hospital, and the Institute of Child Health.

We run clinics for young people who are struggling with over-weight, we call them Weight Management Clinics, not obesity clinics, and I do quite a lot of research into some of the reasons why young people are overweight, and how we can best help them conquer overweight.

People often wonder why we have this problem with obesity now, and that’s a question that’s not always easy to answer. We know that now, around 7-10% of young people are significantly overweight, or what we call obese by certain standards. And we know that in the past its only been about 1% of young people.

We know that people themselves haven’t changed. There’s been no change in the genes. There’s been some change in the background of the British population.We now have many more people whose families came from outside Britain than we did, say 30 years ago, but that certainly isn’t the reason. The reason is that the world has changed around us.

Previously, in the past, our lives controlled what we ate, and controlled our exercise, much more than the modern world does. The modern world, in some sense, stops us being active, stops us exercising and also has a lot more food on offer, that’s much more what we call obesogenic.

People talk about these together as what, as being an obesogenic, or obesity causing environment. And environment that’s somehow toxic to us, where everything is pushing us towards being more overweight. Food is available in every corner, the portion sizes are bigger. For example the Big Macs in Macdonalds have, I think doubled in size since the 1960s. Food is much cheaper, and interestingly, the cheapest food is often the food that’s worst for us.

All the buildings have lifts, where we used to use the stairs in the past.Public transport’s improved. So we do own cars and are much more around. We all have cars now. So there’s many, many reasons, why all the things that controlled our weight in the past, almost we’ve pushed them out of our lives.

There is also some metabolic reasons, and I think we see this particularly strongly in people whose families have a lot of diabetes. That’s certainly true of people whose families come from India, and certain parts of Africa, and the Caribbean. Often those kinds of people have a metabolism which was really well adapted to times when there wasn’t much food around. But that kind of metabolism in the modern world, where food is absolutely everywhere, leads to a tendency to really dramatically put on weight, to be relatively resistant to some of the hormones, like insulin that control blood sugar, and a tendency towards diabetes.So again part of it is our metabolism, but most of it is the world changing around us.

People often wonder about genes, about the genetics of obesity and whether obesity really runs in families.The first thing we know is that being overweight runs very strongly in families. And that part of that is probably due to do with our genetic makeup, the genes we have in our system that help determine our hair colour, our height, and also our tendency to put on weight or not.

And so part of obesity running in families is because of genes, but most of obesity running in families, is probably what we would say is environmental. By environmental we mean that it’s the habits the family has together that tend to make the whole family put on weight. So its complex, its partly environmental, partly genetic.

But for example, families where parents are really very big, often have bigger children. Possibly part of it is due to genes, but mostly because of the eating habits that the family has.

Obesity is undoubtedly partly genetic, but its really important to remember that our genes haven’t changed over the last twenty years, but obesity rates amongst children and young people have tripled. So no change in our genes in the last twenty years, but obesity rates have tripled. I think this is really clear evidence that its about what we eat and how active we are, that’s really led to the obesity epidemic in the last twenty, thirty years, not a change in our genes.

The genes are important, and we are increasing understanding some of the gene problems that cause massive obesity in a tiny number of children, but it’s important to also say that most young people who struggle with overweight and obesity don’t have a genetic problem. Genome problems that really, in a sense force you to be overweight, are very, very rare.

People often wonder about whether other medical conditions cause obesity, and particularly in young women, the condition called polycystic ovarian syndrome is often linked with obesity and young women and their families often wonder whether that causes their overweight and obesity.

I think we’re learning a lot more about polycystic ovarian syndrome and the way it relates to obesity now. And I think what we understand is that polycystic ovarian syndrome is probably a consequence or an outcome of obesity, not the cause of it, in a sense. But it is a bit chicken and egg. We’re not sure exactly which one comes first, but I think the evidence is starting to suggest that it’s obesity largely that drives polycystic ovarian syndrome, not the other way round*. Polycystic ovarian syndrome is a condition where young women’s bodies, their ovaries in particular produce excessive amounts of male hormones. All women’s bodies produce small amounts of male hormones, but a tiny increase in the amount they produce, which happens in polycystic ovarian syndrome can cause excess hairiness, can cause a resistance to insulin.And can cause irregular periods and other problems. And we think that’s mostly a consequence or an outcome of being overweight, not a cause of it.

But it can be really a big problem for youngpeople who struggle with overweight to also have the excess hairiness, and sometimes the spots, and the irregular periods that go with polycystic ovarian syndrome. We know its one of the most distressing things for young women, who are very overweight.

The good news is that getting the weight down, and sometimes using medications that make the body more sensitive to insulin or cut the male hormone levels, can be really helpful in improving both the polycystic problems, but also improving weight.

* Not all young women who developpolycystic ovarian syndrome are overweight.

The body mass index is something that we use to define overweight and obesity in children and young people, and people often ask whether it is the best marker of that.

The body mass index is a way of expressing your weight for your height. We all know that a man whose six foot should weigh more than say a boy who is four foot tall, and one of the ways we have of expressing how high or low your weight is for your height is to divide your weight by your height squared. And that gives you a think called the body mass index or the BMI.

Now the BMI isn’t a measure of fatness. It’s just a measure of total body mass, so the BMI is made up of your muscles your bones, water in your body, and fat in your body.

But of course, if you’re over weight, it’s mainly the excess fat in your body that we’re concerned about, in terms of medical problems, and in terms of also the social issues. So the body mass index isn’t a perfect measure of being over fat. But it’s a good measure of being overweight in that sense.

There are problems with the body mass index or BMI in children and young people, really muscley young people, people who play rugby, or play a lot of sports, can have a high BMI, but actually have low fat levels, and they’re not at all obese, even though their BMI is high, but in general BMI is the best measure of being overweight or obese in young people.

We also use a number of other measures, people measure waist circumference, which is the area around your waist. That’s a really difficult measure in young people, because sometimes it’s hard to know where somebody’s waist is. Is it where their umbilicus, tummy button is, is above that, is it below that. Its really very, you find it very difficult to measure. So we tend to use BMI.

There are other measures, you can use body fat monitors where you hold onto various electrodes and they pass very gentle currents through your body. They’re not really very accurate. They can tell something about the body fat levels, but BMI is the most generally widely accepted measure of overweight and obesity in children.

Now, its important to say that we can’t use the standard adult cut-offs for BMI for children. We know in adults for example if you have a body mass index of over 30 you’re classified as obese, but because children are growing, and their weight and height, and the relationship between weight and height is changing, we have to use different measures.

To be honest for most children and young people having a body mass index over about 23, is usually significantly overweight and obese. But again that changes by age, so we have special BMI cut offs for children and young people, until the age of 18 when we tend to use the adult cut offs.

When talking about levels of obesity, people often use this word, morbid obesity. It’s not a word that we tend to use much in children and young people. In adults they have an easy definition of morbid obesity, which is having a body mass index, or BMI more than 40 kgs per metre squared.Again, in children and young people, BMI is a good measure of general overweight, but it has to be thought about in relationship to the age and sex of the child. And what we haven’t been able to do is identify a clear cut off for what we call morbid obesity in children and young people.

But on the other hand I think it’s not an unreasonable word to use. If somebody is extremely obese, and their weight is affecting their life, it’s affecting their ability to get around, affecting their mental health and well being, and affecting them in other ways in terms of their health, you could call that morbid obesity.

Morbid is a medical word, which means obesity affecting your health to a significant degree.

When young people are struggling with overweight, they often ask me, What can I do to help myself?They say, I’ve tried diets. I’ve tried being more active. But my weight doesn’t seem to change very much.Obesity is both the most difficult thing for us to manage in our lives, or one of the most difficult things, but in a theoretical sense, its actually very simple, and balancing the simplicity of the theory with how difficult it is to change our lives can be hard for young people.

We know that, in one sense, what you weigh, and your body mass index, is a balance between the amount of calories, or energy that you eat, and the amount of calories or energy that you burn up.And in a very simple way, what we call the energy balance equation, if you eat more calories than you burn up, you will tend to gain weight.And if you burn up more calories than you eat, you will tend to lose weight, or lose BMI.

Now that sounds really very simple. And it’s easy to think just change your balance, but we know changing the balance, your energy balance in your life is really very difficult, partly because of the way the world around us pushes us to be overweight and obese.

People ask me, Do interventions or treatment for obesity work?The answer is, Yes, they do.We can get very pessimistic and say nothing works very much.But there’s lots of evidence that actually if people change their lifestyle over a long period, they can lose significant amounts of weight.

Dieting doesn’t work.It tends to put on weight in the long term. Over-exercising doesn’t work. But a general change, healthy lifestyle, healthy activities, can make a real difference long term.

There are a whole range of programmes available in the community now that help people develop their self esteem, think about changing, and actually make changes to their life. And actually it’s the psychological element of many of these programmes that’s more important, than the actual diet, than the actual healthy eating you learn about or the activities that you do.

People make all sorts of assumptions about young people who are overweight, over eating. Many young people don’t over eat at all. But are still overweight, and again it goes back to their energy balance equation. If the amounts of food, the amount of calories that you take in, is balanced with the amount that you burn up, your weight doesn’t change. And that’s true whether you’re very skinny, or very overweight. So you could be a very big eater and do a lot of activity but if you’re in balance you’re weight won’t change, and that’s true if you’re very skinny, or very overweight.

The way most people become overweight is to be a tiny, tiny bit in positive energy balance, every day. What I mean by positive energy balance is that they eat and consume a little bit more energy or calories than they burn up, every single day on average. The amazing thing is if you’re positive by just twenty calories a day, it’s about the equivalent to a spoonful of butter, or a bit of extra butter on your bread, if you do that every day for a year, you’ll put on almost a stone in weight. It’s amazing to think of that.

And this is how most people, most young people become overweight over time, they are just a tiny bit positive every day. They’re not huge over eaters, they’re not lazy slobs, they’re just a tiny bit in positive balance every day.

Now in one sense, that’s really good news to think about, because actually that means that tiny differences, can make a big difference. If you manage to get yourself into balance, your weight won’t change, so rather than be 20 calories positive every day, just be in balance.But if you’re 20 calories negative every day, on average you might lose a stone, which is about 6kgs over a year.

And that’s really very important, tiny changes can make a big difference. When young people say to me, Look I’ve really tried exercising, or being more active. I went to the gym for three weeks. Or I’ve tried dieting.I think part of the problem is, they’re still out of balance, that’s number one, or number two, actually it hasn’t gone on long enough. You really need to be able to change your activity levels, to be healthily active and change your eating to be healthy eating for really quite long periods. Many months to really see change.

It’s important not to diet. It should be about healthy eating, not dieting. We know, it’s strange but true, dieting tends to make young people put on weight. You could lose weight in the short time, but if you look at young people who diet, some months later, or years later, they almost always weigh more than they did before they start dieting. So it’s not about dieting. It’s not about madly going to the gym. It’s about changing our energy balance over a long period, to be more healthily active, and to eat more healthily and to try and get tiny changes, that rather than gradually gaining weight, we lose weight. They are the things we can do to help ourselves.

You can’t do it by yourself. Having parents around you and friends around you, who are supporting you, is absolutely key. You can get help from health professionals, from your local GP, practice nurses, your paediatrician or others. People are there to help you make those changes.

One of the good things about children and young people is that they grow, and one of the really important things about growing is that you can grow into your weight. If you’re a 6 year-old and you’re quite overweight, what we don’t recommend is losing weight in general. What we recommend is kekeeping your weight steady and just growing. Because the wonderful thing about [um] growing children, is that you can grow into your weight over a couple of years. And there’s lots of successful examples of young people, who over a couple of years, keep their weight steady. They just stop increasing, they don’t lose weight, and actually a couple of years later, they’re really grown into their weight, and they are a much better weight and shape.

There’s a question about whether weighing and measuring is very accurate, and how repeatable it is. Certainly many young people have the experience of putting themselves on their scales every day, and they can be up half a kilo, or down a whole kilo day by day, and sometimes they think that weighing and measuring is not very accurate.

Part of this is very true, your body weight will go up when you have a full bladder, or you haven’t been to the loo, and have a full bowel, and it can go down, after you’ve just been to the loo. You can even lose a kilo and a half just by going to the loo. So our body weight can change like that.

The important thing about measuring somebody’s weight over time, is to do it accurately once, and then not to do it too frequently. Certainly your height for example, those of us who measure children’s height, often know that its inaccurate to measure it more than every three months, because our height changes a bit depending on how our posture is, whether we’re measured in the mornings or the evenings etc.So you can’t really tell if somebody’s grown for up to three months.

Weight can be measured much more frequently, but we certainly wouldn’t advise people to weigh themselves more than once a week at the absolute outside. Under that you risk getting inaccurate results, and also slightly being obsessed about your weight.