Their conclusions, published in a joint paper in the September issue of Diabetes Care (vol 28, issue 9, pp2289-304) and Diabetologia, will come as a warning to health food makers increasingly interested in offering products to tackle the condition.
The American Diabetes Association and European Association for the Study of Diabetes argue that the metabolic syndrome - which has come to be regarded as a predictor of cardiovascular disease - is poorly defined, inconsistently used and in need of further research before doctors diagnose it in patients.
"We shouldn't be diagnosing people with the 'metabolic syndrome.' Doing so misleads the patient into believing he or she has a unique disease. What they really have are well-known cardiovascular risk factors," said Richard Kahn, chief scientific and medical officer of the American Diabetes Association, in a statement last week.
He added: "The combination of risk factors does not add up to a more significant or higher cardiovascular risk than the individual components."
However Professor Sir George Alberti, the past president of another diabetes organisation, the International Diabetes Federation (IDF), says that a number of studies, including the Framingham trial and a major trial in Glasgow, have clearly demonstrated that a combination of risk factors raises the likelihood of heart disease.
But he added that debate is normal with evolving concepts and agrees that the definitions of the syndrome are so far inconsistent.
"They [the ADA and EASD] criticize the old definitions of the syndrome, as we did, which is why we came up with a new one earlier this year," he told NutraIngredients.com.
The metabolic syndrome is often defined as having any three or more of the following: a large waist circumference; high triglyceride levels; high blood pressure; low HDL cholesterol; and high blood glucose levels.
But the World Health Organization offers a different definition, including anyone who has diabetes or insulin resistance and two of the following: high waist-to-hip ratio; high triglycerides or low HDL cholesterol; high blood pressure; and a high urinary albumin excretion rate.
In April, the IDF said it had gathered experts from six continents to produce a consensus definition. This requires that a person has central obesity, plus two of four additional factors: raised triglycerides, reduced HDL cholesterol, raised blood pressure, or raised fasting plasma glucose level.
But the ADA and EASD say that these conflicting definitions mean there is no clear evidence base for what should or should not be included in research into the condition.
Doctors should focus on treating the individual heart disease risk factors, rather than a combination.
Yet while the medical professionals struggle over how, and whether at all, they should be treating metabolic syndrome, Professor Alberti believes the numerous definitions have a positive impact.
"Regardless of what we know, it's a way of getting health professionals to focus attention on cardiovascular risk factors," he said.
There is certainly a need to deal with heart disease risk. The use of different definitions has made it difficult to estimate the prevalence of metabolic syndrome although recent data from Australia and the US provides a broad estimate of 20-25 per cent of the adult population, according to the IDF.
But there are clearer figures for diabetes - the US' fifth cause of death by disease - and heart disease, the world's number one killer, according to WHO.
Ingredient firms like Frutarom, Indena and Degussa, which have all recently launched new products that are designed to target metabolic syndrome, or specific cardiovascular risk factors, may find it difficult to encourage food makers to market these ingredients to help reduce metabolic syndrome, given the current debate.
Yet it is widely agreed that prevention of the syndrome, or its different elements, should be through nutrition.
"The first step is very much strong nutritional advice to people. That combined with increased physical activity could deal with 90 per cent of people with the syndrome," said Professor Alberti.
Professor Alberti also welcomed the paper's call for further research into metabolic syndrome and its recommendations that doctors continue to evaluate, and 'aggressively treat' individual cardiovascular risk factors.
"They're taking a more academic approach, and it's a good thing to promote more research. But the IDF represents a more practical approach. This definition is a good way of picking up people who are at risk of heart disease without having to do any tests," he said.
"A tape measure is as simple as you can get. For people in developing countries especially, we can do something for them [using this definition]," Professor Alberti added.