Rivalries between older siblings and younger siblings are not a new concept, but a new study has revealed that firstborn women may actually have a good reason for envying their younger sisters.
Swedish researchers have conducted new research and concluded that firstborns are more likely to be obese, or at least overweight. In fact, they have even reached a statistic – firstborn women are and 40 percent (40%) more likely to be obese, compared to second-born women, and 29 percent (29%) more likely to be overweight, compared to second-born women.
This is not the first study to suggest that firstborns are at risk of becoming obese, however it is the largest one.
To reach these conclusions, the research team looked at almost 13.500 pairs of sisters from the Swedish Birth Register. The data examined included the weight that each subject had when she was born, and the weight and height that each of them had when she was pregnant for the first time.
The experts noticed something interesting. On average, firstborn women weighted a little less at birth, compared to second-born women. However, things changed when they were in their first trimester of pregnancy – firstborn women had slightly higher body mass index (BDI). Older sisters averaged at 24.4, while younger sisters averaged at 23.8.
According to Dr. Wayne Cutfield, senior author and professor of endocrinology from the University of Auckland (New Zealand), this is a significant difference. He gave a statement saying that “This study backs up the findings of three (3) earlier studies conducted by [the research team] in adult females, adult males and children of both sexes”. All three (3) of them concluded that firstborn men and women are predisposed to becoming obese or overweight.
The research could not prove why older siblings are more likely to have trouble with their weight, however Dr. Cutfield and his colleagues have their theories. One of them is that the blood supply reaching the placenta may change after the first pregnancy and affect how fetuses develop in the womb.
The fetus from the first pregnancy may get a limited blood flow. If this is the case, then the developing baby may get fewer nutrients, which in turn reprograms their fat and glucose regulation, and later in life, the individual becomes more likely to store fat and have insulin that doesn’t work very effectively.
This may also make them vulnerable to developing type 2 diabetes as insulin resistance is a risk factor of the disease. It works by preventing an individual’s body cells from using insulin effectively.
Based on this line of thought, the Swedish researchers went on to theorize that the increasing number of small families (couples who only have one child) may contribute to the increasing rate of obesity as there are a lot of firstborns and very few second-borns.
But they also stressed that being the older sibling is only a small part of the equation. A healthy diet and regular exercise can always keep people from becoming obese or overweight.
The new study was published earlier this week, on Wednesday (August 26, 2015), in the Journal of Epidemiology and Community Health.
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