This is incorrect. Your behaviour changes your environment (both directly and/or by exposing you to new/altered environments) and your environment modifies how your genes are expressed. See the wikipedia page for Epigenetics:
"Epigenetics [...] is the study, in the field of genetics, of cellular and physiological phenotypic trait variations that are caused by external or environmental factors that switch genes on and off and affect how cells read genes instead of being caused by changes in the DNA sequence. Hence, epigenetic research seeks to describe dynamic alterations in the transcriptional potential of a cell." [1]
These mechanisms act on an individual and are separate from Darwinian adaptation.
[1] https://en.wikipedia.org/wiki/Epigenetics
EDIT: "and your environment modifies your genes" -> "and your environment modifies how your genes are expressed"
The Danish/ Swedish famine study that first proved epigenetics was real showed that starvation during puberty affected the height of granchildren by switching off genes that were still present. The third generation is unaffected precisely because it is not genetic change.
Enviroment only affects genes by reproduction, successful genes are inhereted or not - there is no change in genes during a lifetime - that would be Lamarkism and he was wrong.
Lifestyle affects methlyation markers,which are added and change gene expression for a few generations.
The underlying genes are not changed and are still inhereted, once the methlyation 'wears off' everything will be as before.
It just does not work that way. Mutations could be favorable and unfavorable, but there is no mechanism that "adaptations" are encoded back into genome.
Some random mutation which persisted in one population and wiped out in another has been selected due to environmental factors, such as climate and availability of food sources, does not imply that it is necessarily better or advantageous for a different environment.
And, of course, a diet could not cause genetic changes. Mutations could be selected in a population within some particular environment or wiped out in another.
[1] http://www.medicalnewstoday.com/articles/247104.php [2] http://www.eurekalert.org/pub_releases/2015-09/elf-gsh092515...
"Widespread vegetarian diets among a population could cause changes over time" is wholly different and apparently more accurate.
http://mbe.oxfordjournals.org/content/early/2016/03/09/molbe...
It's worth pointing out that here "genetic changes" means evolutionary adaptation over many generations, not some sort of mutagenic effect
But last week red meat gave us colon cancer!?!?
