New research from India links higher birth weight to leaner adults.
The study was done in India, in a culture quite different from the mainstream U.S. But if the findings check out, it could mean that being born big or becoming big in early childhood predicts adult leanness.
The study appears in The American Journal of Clinical Nutrition. It was led by researchers including Harshpal Sachdev, MD, of the pediatrics department at Maulana Azad Medical College in New Delhi.
The study spanned more than 20 years. In the late 1960s and early 1970s, measurements were recorded for more than 2,500 newborns in Delhi, India.
Follow-up was done at six months, one year, and every six months after that until age 14-21 years. More than 1,500 participants got one last check when they were 26-32 years old.
Besides stepping on a scale, their height, hips, waists, and arms were measured. They also got skin-fold tests of their arms and shoulder blade area to measure body fat.
Body mass index (BMI) is a measure used to define overweight and obesity, which uses height and weight measures. Obesity has many health consequences — including increasing the risk of heart disease and diabetes. However BMI does not distinguish between lean and fat components of body weight, and body composition can vary at any given BMI, the researchers write.
South Asians have a low average BMI but a higher percentage of body fat; they also have more fat located at the belly (central obesity — a risk for heart disease). The researchers say this may partly explain why this group has a higher risk of developing type 2 diabetes and heart disease — despite the low average BMI.
They say that weight gain at different periods of early life may have different effects on the acquisition of fat and lean mass. "There is good evidence, for example, that higher birth weight is associated more strongly with adult lean body mass than with adult adiposity (fat tissue)."
A few facts stood out for the 1,500 participants who finished the long-term study:
· Average birth weight was about 6.3 pounds
· More than half were underweight as 2-year-olds
· As adults, 47 percent were overweight, 11 percent were obese, and 51 percent were obese around their midsection
Overall, bigger birth weights were tied to adult leanness. Rising BMI in infancy and early childhood followed the same pattern.
But, BMI gains in late childhood and adolescence forecast adult fatness, the study shows.
In women only, birth weight was linked to adult fat tissue — but not fat waists, the researchers write.
Window on a Different World
Participants grew up in circumstances unfamiliar to many Americans.
At the study's start, six out of 10 families had a monthly income of more than 50 rupees, compared to the national average of 28 rupees per month. In addition, only 15 percent of participants' parents were illiterate, compared with India's national average of 66 percent, at the time.
Still, more than four out of 10 participants grew up in families that lived in only one room. Since the U.S. dollar is (and was) stronger than the Indian rupee, many families lived on a fraction of typical U.S. incomes.
The researchers noted physical activity, smoking, alcohol use, and participants' possessions. Their list of 17 items included electricity, fan, bike, radio, TV antenna, car, computer, air conditioning, and washing machine.
Leaner adult participants had fewer belongings. Those with less than six items had a BMI of 20.5 (low, yet normal weight), compared with a BMI of nearly 27 (indicating overweight) in those owning 15 or 16 possessions.
SOURCE: Sachdev, H. The American Journal of Clinical Nutrition, Aug. 1, 2005; vol 82: pp 456-466.