More evidence for 5 a day

Scientists funded by the US government science agency, the Agricultural Research Service, studied volunteers' everyday eating habits to better understand dietary causes of obesity, a health condition that has reached epidemic proportions globally.

The UN-backed World Health Organisation estimates that today, there are more than 1 billion overweight adults, and at least 300 million of them obese, in the world.

Obesity and overweight pose a major risk for chronic diseases, including type 2 diabetes, cardiovascular disease, hypertension and stroke, and certain forms of cancer. The key causes are increased consumption of energy-dense foods high in saturated fats and sugars, and reduced physical activity.

In this latest study​ conducted by a post-doctoral student P. Kirstin Newby and overseen by Katherine Tucker at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston, the scientists looked at the food consumption habits of 459 healthy men and women participating in the ongoing Baltimore Longitudinal Study on Aging.

Diet types were assessed using a 7-day dietary record, from which five dietary patterns, or 'clusters,' were derived. These dietary clusters were labelled as 'healthy', 'white bread', 'alcohol', 'sweets', and 'meat and potatoes'. The names reflect the foods that contributed relatively greater proportions of caloric intake in each cluster.

Publishing their findings in a recent issue of the American Journal of Clinical Nutrition​, the scientists report that overall, those in the 'meat and potatoes' cluster gained more weight than those in the 'healthy' pattern. Individuals in the 'alcohol' pattern consumed about 15 per cent of their daily calories as alcohol, compared to only about 2 to 3 per cent for people in the other patterns. And those in the 'sweets' pattern consumed about 11 per cent of calories from high-fat baked goods, such as cakes, muffins and biscuits, which is about twice the amount consumed in the other patterns.

Those in the 'sweets' pattern also consumed about 10 per cent of their calories from high-fat dairy foods.

Today, body mass index (BMI) is often used to determine obesity, rather than the height and weight charts used in the past. A BMI of 25 to 29.9 suggests overweight, while a BMI of 30 and above reflects obesity.

While BMI is a common measure used to indicate body fat, waist circumference is a common measure used to indicate abdominal fat. Excess fat in the abdomen, independent of total body fat, is considered a risk factor for ailments associated with obesity, such as diabetes.

According to ARS​, the mean annual change in waist circumference found in the study was about three times greater for volunteers in the 'white bread' cluster than for those in the 'healthy' cluster. The white bread group ate about 16 per cent of their daily calories as white bread or refined grains, which is almost five times greater than that consumed in the healthy group. While those in the healthy cluster gained an average 1/6-inch in waist circumference per year, those in the white bread, alcohol, and meat and potatoes clusters gained close to a half-inch per year.

"The interesting point here is that those in the 'meat and potatoes' group gained in both waist circumference and BMI, while those in the 'white bread' group - and to a lesser extent, the 'alcohol' group - disproportionately gained waist circumference relative to BMI,"​ said Tucker. "Because gains in waist circumference are particularly related to greater health risks, it's important to monitor changes in waist circumference as well as total weight gain, and to try to minimise abdominal weight gain."​

The study's authors conclude that eating a diet high in fruits, vegetables, reduced-fat dairy products, and whole grains - and low in red and processed meat, refined grains, fast food, and sweetened soft drinks - is associated with smaller gains in both BMI and waist circumference.