The top reasons nutrition “science” flip flops:
1. Effective advice differs based on the goal. Weight loss, general health, and fitness performance have different requirements. You can certainly achieve more than one at a time, but advice for one often doesn’t take the others into consideration. Hence, many personal trainers give unhealthy nutrition advice while many holistic health coaches give advice that isn’t great for athletic performance.
2. Science is reliable. However, human interpretations of scientific research are often flawed, and reports of those interpretations often sensationalized in the media, especially when certain interpretations make for better clickbait or profits.
3. Building on #2, nutrition is bioindividual. Most scientific studies look at groups, and too often these groups aren’t representative of society. What worked for the majority in the study becomes the basis for advice for the general population, even if a large minority saw different results.
4. Practitioners often give watered down advice if they don’t believe that people will actually do what science shows is most effective.
What others can you think of?