Need stata command for a question

[Dysfunctional1017]

The NHS has been promoting the “5 a day” campaign recommending individuals to eat five portions of fruit and vegetables a day. Is there any evidence that eating higher proportion of fruits and vegetables improves BMI? 

What would be the stata command for this question?

[J]

You can use OLS (regress command in Stata) to look at the correlation between BMI and eating fruits and vegetables. However, this won't answer your question which poses a causal question. Does eating vegetables cause lower BMI?  To answer that you need some exogenous variation in the consumption of fruits and vegetables. This isn't a command in Stata, but rather necessary identifying variation in the data. 

~J