For years, it has been assumed that obesity is the result of "too much food and too little exercise". While this maxim is largely correct, the etiology of obesity can be much more complex. There is a well-documented familial tendency, but whether this is of environmental or genetic origin is unclear. Studies of twins separated at birth and living apart provide strong evidence for a substantial genetic influence. Children of overweight parents, when adopted by "lean" families, have a greater tendency to become obese than do adoptees from nonobese natural parents. "Energy efficiency" may contribute to obesity; with reserves of fat deposits readily available to metabolize in the obese, a given amount of activity requires a smaller expenditure of energy. This theory has been invoked by those who complain that they "gain weight whether they eat or not", and indeed there is evidence of differences in energy efficiency among individuals. Similarly, obesity has been attributed to abnormally low basal metabolic rates (BMRs) since obese individuals do show lower BMRs. However, this fact is due to an artifact of BMP measurement; a larger proportion of the total fat mass of an obese person is inert, low-metabolizing fat, a fact that makes BMR calculations lower.
The main idea of this passage is ___.
to discredit the idea that there is a greater degree of energy efficiency in the obese
that the environmental and the genetic causes of obesity are more or less the same
to establish that the factors behind obesity are highly complex and even contradictory
that obesity is a serious health hazard and that a great deal more research into the treatment of it is required
to impress on overweight parents the need to watch their children's diet and life-style
According to the passage, the theory that obesity has a strong genetic basis ___.
seems more likely than the one concerning the BMRs
is slowly falling into disfavor and being replaced by one that puts the emphasis on energy efficiency
has not so far been well researched, but as it is the most likely theory, it deserves to be
is supported by some studies of twins that have been brought up separately
is soon likely to be fully substantiated
The passage suggests that the theory that obesity is due to a low BMR ___.
has never had any serious recognition
needs to be reconsidered as the manner of calculating this rate in the obese is inaccurate
has been invented by the obese who claim that the amount they eat makes no difference to their weight
will probably turn out to be the correct theory
has been thoroughly researched in several cases of twins