NHS Greater Glasgow and Clyde has awarded a two-year contract to provide weight management services to Weight Watchers following a tendering process.
The health board said the use of Weight Watchers does not replace its own weight management service while funding for the pilot has not been diverted from any existing services.
A statement from NHS Greater Glasgow and Clyde said: "This new development is being piloted to enhance the existing arrangements to support patients with weight management.
"None of the funds for this pilot are being diverted from the current hospital-based weight management service - this is a separate community service for those who require less intensive support. In addition, this pilot does not replace any other NHS community weight management service in the Glasgow and Greater Clyde area."
The scheme will target patients who are at risk of developing health complications as a result of their obesity. It could include patients who are borderline diabetic or whose blood pressure put them at an acute risk of stroke. The pilot's success will be evaluated after two years.
It is the first time the slimming club has been used by the health service north of the Border, but GPs in England have been able to refer obese patients to Weight Watchers since 2008. Around two thirds of NHS Trusts in England can send patients to the classes, which cost private members around £45 for three months.
Figures published last year revealed that the arrangement had cost the health service in England £4 million over five years.
The largest study so far of a commercial weight-loss programme found that one third of almost 30,000 people who were referred to Weight Watchers lost five per cent or more of their bodyweight.
However, its success as a long-term public health intervention has been called into question.
Dr Carl Heneghan, an expert in evidence-based medicine at Oxford University, found that only 11 per cent of patients who took up the offer and achieved their goal weight managed to maintain the weight loss two years later.
Zoe Griffiths, head of programme and public health for Weight Watchers UK, said: "Weight Watchers has been supporting local health bodies and providing successful weight management on referral services since 2005, and has worked with over 100 public health and NHS organisations across the UK."
A Scottish government spokesman said: "NHS Scotland does not promote competition and makes very limited use of the private sector to provide targeted services.
"The most recent figures show that NHS Greater Glasgow and Clyde spending in the private sector for services has fallen in recent years and stands 0.8% of their frontline budget, and is projected to fall further."
"NHS Greater Glasgow and Clyde are working with Weight Watchers on a community-based pilot project, which will be in addition to their existing hospital-based weight management service"