By Jane Elliott
BBC News Online health reporter
Getting children to change their eating behaviour and exercise levels is notoriously difficult.
The Zaman family have changed their lifestyle
But a new project is encouraging overweight children to gain the self-confidence to start making changes by building a better environment for others.
Deep in the wilds of Hackney, in a little corner of a piece of reclaimed wasteland, five overweight 11-year-olds are getting stuck into a project to build some nesting boxes for the local population of bats.
It is a far cry from the image of couch potato children who do no exercise.
Melissa is one of those taking part in a new BTCV (formerly British Trust for Conservation Volunteers) project for Hackney Ground Zero.
She and her mother have long been worried about her weight and how little exercise she had been taking.
She is already seeing the benefits from the project which started in January.
She has started to take more exercise and eat a balanced diet.
Melissa said getting involved in conservation was a great way for her to start taking exercise.
"This was something different to do and it is good for the environment as well.
"It is hard work and I do feel tired, but I feel like it has all been worthwhile and I do get satisfaction from it.
"I was worried about my fitness, and although I did not get much teasing about my weight I did need to get some confidence.
"By doing this I have met people who are overweight like me and I am getting more confident."
As well as encouraging more exercise, the pilot scheme offers nutritional advice, one-to-one mentoring and four family holidays a year.
The emphasis is very much on including the whole family and Melissa's mother Nima Zaman said she was also benefiting.
Melissa loves the conservation work
"I have a lot of problems with my own health and have diabetes and heart problems so wanted Melissa to be fitter and more healthy.
"I know it was a problem of lifestyle. We did not exercise enough."
She said her daughter, who at 5' 2'' tall weighed in at 12 stone, was not eating a healthy enough diet, and Nima blamed herself for this.
Hackney Ground Zero, she said, had taught her about healthy choices so she could start to share them with Melissa.
"We have changed the way we eat, and we are eating more fruit and vegetables and salads and less fats."
Ellie Mortimer, of BTCV, said it was too early to say whether the project would produce long-tem benefits - but if the year-long scheme is a success it is possible the same formula will be adopted across the country.
She said it was an excellent way of encouraging children who might not try traditional sports to exercise.
"I think a lot of kids are not active enough for many reasons. They might not enjoy the traditional sports or they might not be able to access them.
"This is a bit different from the sports they do at school. Everyone here is the same and there is no bullying.
"The atmosphere we provide is very encouraging and they do get to make something at the end of the sessions.
"People do not think this is going to be very strenuous, but it is and you get very tired. We do warm-ups and cool-downs after the sessions."
BCTV already run a similar scheme for adults called the "green gym".
The children build bat boxes
Hackney Green Ground Zero specifically targets 11 and 12-year-olds because this is thought to be a good age to effect change.
Professor Jane Wardle, director of the Cancer Research UK's, Health Behaviour Unit, based at the University College London, said schemes like this were important to get children back into the way of exercising.
"There is lots of evidence that children are not exercising enough and quite a lot of evidence that children who are obese are doing even less than the rest."
She said that exercise alone might not reduce weight, but that it would help as part of a plan including nutritional advice.
"This seems to me like a fantastic idea. They are doing something to move around, rather than being sedentary.
"There is a huge amount of research on the difficulty of getting children and their families to change their diet.
"The important thing for families is to move to a healthy way of eating rather than the child going on a fad diet."
She said that obesity in childhood could result in many problems in later life as obese children often tend to be obese or over-weight adults, running the risk of heart disease, diabetes, cancer and joint disorders.