Certain participants in the Swedish overfeeding study showed apparent resistance to becoming "supersized" despite excess food intake (27 January, p 28). This should be no surprise.
A number of experiments with pairs of identical twins have reported that twins gain almost exactly as much weight as each other, though there are marked differences between pairs of twins. This suggests that genetics play a large role in determining responses to chronic overfeeding.
The same variability is seen in responses to weight-loss interventions through diet and/or exercise. Clearly, not every person who consumes excess calories will become obese, and conversely not every overweight person who diets and exercises will experience identical weight loss.
It seems that during past times of food scarcity, "thrifty genes" ensured survival. Unfortunately, these same genes now contribute to the development of obesity in our current "obesigenic" environment.
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