A) Obesity is HIGHLY heritable. Tons of twin and adoption studies prove this. The correlation between the adult BMIs of adopted (non-related) siblings raised in the same household is virtually zero. This means that parenting practices have no long-term impact on body fatness. The correlation between the adult BMIs of biological siblings raised in different households is strong, though.*
B) Virtually all attempts to lose weight eventually fail. "Eat less and exercise more" essentially doesn't work as a long-term weight loss intervention, because very few people are able to comply with it over the long term. The one exception is gastric bypass surgery, which does reliably produce long-term weight loss. There are some new medications that show promise, but it's too soon to tell if they'll work permanently.
*People will inevitably say "how can obesity be heritable when it's increased so much over time? Americans used to be much thinner!" But the same is true of other highly heritable traits, like height. In some Asian countries, people are six inches taller than they were 100 years ago. Nevertheless, height is heritable. Heritability exists within a specific environmental context, and our environment is much more conducive to obesity than it was in the past.
It's not clear, although it seems reasonable to assume that the availability of cheap processed food is a major factor.
If changing one's environment were a straightforward thing, like changing what foods one keeps in one's cabinets, then the data on the effectiveness of weight loss interventions would not be so dismal. An effective change of environment is probably more like "moving from Alabama to Japan".
A) Obesity is HIGHLY heritable. Tons of twin and adoption studies prove this. The correlation between the adult BMIs of adopted (non-related) siblings raised in the same household is virtually zero. This means that parenting practices have no long-term impact on body fatness. The correlation between the adult BMIs of biological siblings raised in different households is strong, though.*
B) Virtually all attempts to lose weight eventually fail. "Eat less and exercise more" essentially doesn't work as a long-term weight loss intervention, because very few people are able to comply with it over the long term. The one exception is gastric bypass surgery, which does reliably produce long-term weight loss. There are some new medications that show promise, but it's too soon to tell if they'll work permanently.
*People will inevitably say "how can obesity be heritable when it's increased so much over time? Americans used to be much thinner!" But the same is true of other highly heritable traits, like height. In some Asian countries, people are six inches taller than they were 100 years ago. Nevertheless, height is heritable. Heritability exists within a specific environmental context, and our environment is much more conducive to obesity than it was in the past.