Is it ethical to deliberately provide incorrect information to participants in a psychological study? I've noticed that several psychological studies purport to measure one thing, but once participants enroll, they end up measuring something completely different.

For example, I recently came across a study where participants were told that the study was meant to help create personalized nutrition and exercise programs. The participants were then given fake DNA test results and what was actually measured was their response to the placebo effect of the test results.

What are the ethics of this? Don't such studies make it less likely that people will enroll in such studies in future and degrade the scientific endeavor in general? Is there no way for psychology to make progress without lying to unwitting study-participants.
The whole point of these lies is to prevent participants from changing their answers because they want to please the researchers or convey their personal beliefs about a topic.

It is typical to inform participants about the true purpose at the end of the study if this is possible. Other times, studies use purposefully vague language in describing the purpose. The point is to provide enough informed consent for participants to agree to the bounds of what a study will ask of them.

All of these decisions about study design are reviewed by an Institutional Review Board that is in charge of research ethics at an institution. Yes, these sorts of lies are ethical.

As far as your specific example, how would you expect a study testing placebo effects to work if you started the study by telling the participants "This is a study about the placebo effect"? - knowing it is a placebo ruins the whole idea of the placebo effect.