A few extra kilos won't hurt you - US govt study

Overweight people are less likely to die in any given period than people of normal weight, according to a US government study published in the Journal of the American Medical Association this week.

The study is not a ticket to break your New Year resolution.

It found that if you are grade 2 or grade 3 obese - or at the fattest end of the body mass index (BMI) scale - you are more likely to die than a person of normal weight during any given period.

But if you are grade 1 obese, you are actually 5% less less likely to die than a person of normal weight during any given time period.

And if you are merely overweight, you are 6% less likely to die.

Doctors say there is overwhelming evidence that eating properly and exercising are good for your health.

Yet the study the study highlights the so-called "obesity paradox" - that overweight or grade 1 obese people suffering heart disease, diabetes, hypertension and kidney disease have less chance of dying during a given time period than fellow suffers with a normal BMI; possibly because of their greaer metabolic reserves.

The Study used the US National Heart, Lung, and Blood Institute's terminology with categories of underweight (BMI of <18.5), normal weight (BMI of 18.5-<25), overweight (BMI of 25-<30), and obesity (BMI of ≥30). Grade 1 obesity was defined as a BMI of 30 to less than 35; grade 2 obesity, a BMI of 35 to less than 40; and grade 3 obesity, a BMI of 40 or greater. Work out your Body Mass Index number with the BMI calculator on the NZ Heart Foundation website here.

Its findings suggest that blood pressure, blood sugar, cholesterol, triglycerides, waist circumference and strength and endurance tests are better measures of health than the weight-focused BMI.

One problem with BMI is that it treats all weight equally, be it good fat, bad fat or muscle - which is why it can be a misleading metric for sports people and others who are fit.

The peer-reviewed study was carried out by researchers at the US government's Centers for Disease Control and Prevention (CDC). It examined the results of 97 studies from around the world involving three million people and 270,000 deaths. Read the full results here.