The $1million study - the largest in New Zealand - will be announced by representatives from the Maurice Wilkins Centre at the annual Queenstown Research Week today.
Study co-director and Maurice Wilkins Centre deputy director Peter Shepherd, of the University of Auckland, said it would be the first time scientists would ''drill down'' into genes to find specific mutations.
That could enable testing to determine a person's susceptibility to obesity.
''The devil will be in the detail,'' Prof Shepherd said.
''It will be the exact mutations that people have that will dictate the biology ... this idea that we could all be skinny if we wanted to is probably not true.
''There are people at one end of the spectrum and there are people at the other end of the spectrum and genes play a big role in that.''
The study is being supported by Giles Yeo, an obesity expert from the University of Cambridge who is presenting his work in Queenstown this week.
Dr Yeo is also a presenter of BBC documentary The Perfect Diet for You, which attempts to match people's genetics with an appropriate diet to try to achieve better long term weight loss.
He told the Otago Daily Times yesterday he had been working in the obesity field since 1998, initially looking at rare ''single gene defects'' causing extreme obesity.
About eight years ago, he turned his attention to ''the 99%'' who do not suffer from that.
''One of the things which people always [say] when I say I study the genetics of obesity is I [have] become a bad person, because they think I'm giving people an excuse; I'm giving people a genetic crutch.
''And I'm not.''
He said genetic predisposition was like being dealt either a good or bad poker hand. Either could win or lose.
''How you play your hand in genetics is your lifestyle - the choices you actually make within that scenario.''
Dr Yeo said it was widely known ''the only way you can make fat become obesity'' was for a person to eat more than they burned off in energy.
However, studies indicated obesity was influenced by genetics, specifically why people eat more.
While obesity was a worldwide concern, wider issues were morbid diseases it contributed to which were overwhelming health systems, for example, cardiovascular disease, arthritis, cancer and type 2 diabetes, Dr Yeo said.
Prof Shepherd said scientists hoped to find a range of genes to give ''a fingerprint'' of obesity and, from there, develop interventions ranging from diet and exercise, to medication and surgery.
The study had now been approved and scientists would soon be taking blood from the first of the patients with initial results expected early next year.
Tony Merriman, of the University of Otago, will be the co director responsible for genetic analysis, using the university's significant genetics expertise, as well as his experience studying the genetics of gout.
Dr Merriman said the study was feasible in New Zealand thanks to advancements in the technology used to analyse genes.
''Our experience in studying the genetics of gout suggests that the new study has a high chance of finding important new information that can be clinically useful.''
