From Penny Johnson
You suggest that having a fat tummy may shrivel your brain (8 January, p 14). But an alternative explanation could flip this theory on its head: perhaps the brain changes in obese individuals are the cause of obesity, rather than the result.
The editor writes:
• The study we reported showed a correlation between brain changes and obesity, but it is not known which comes first. A prospective, longitudinal study would be required to establish a causal relationship.
Carnforth, Lancashire, UK
