In a TED Talk Tim Noakes, MD says "...fifty percent of what we teach is wrong, but the problem is we do not know which fifty percent it is". I suspect that there is no more area in which this is true than when it comes to nutrition.
For a fitness professional, and really anyone else really, nutrition is so confusing. Listening to media reports that seem to contradict what you heard a few days before muddies the water. I think this leads a lot of folks throwing up their hands and eating what they were eating before. What I will present below might be controversial to some.
1) I think the idea that any one diet will work for everyone is silly. The variation in humans is great enough that the idea that ever person on Earth should eat the exact same diet is foolish. Now I will admit that at one time I did hold onto the idea that diet guidelines could be applied to everyone. Some people do not digest or process some foods as well as others. Native Americans, for the most part, do not synthesize alcohol as well as Europeans. So would you recommend a daily drink for them? What about lactose intolerant folks? Would you recommend milk? Or those with legitimate gluten issues? Would you recommend a high grain diet?
2) Everyone has an ideal diet. The trick is finding it. Also what makes an ideal diet? My take is that it is a diet that reduces markers for cardiovascular disease, diabetes and other chronic disorders. For some people performance needs might also need to be considered. How do you find the diet that works best for you? Trial and error and data gathering. Before making a change, get blood work done to look at cholesterol, triglycerides, etc. After trying a diet for a sufficient period of time (let's say 90 days minimum), get blood work done again to see if there are changes.
3) Do not demonize food. No foods are bad foods (okay except maybe cauliflower). Have a piece of cake on your birthday! Of course, eating cake every day is probably not a good idea. Fat is not evil, and neither is gluten. The number of people who are truly gluten intolerant in the United States is pretty low.
4) Eat when you are hungry not because the clock shows a certain time. (Here is an area where athletes training is going to vary, but that is a small group of people).
About 1.5 years ago I was approached by a woman (I will call her Ketogirl) who had just started low carb, high fat (LCHF) and wanted to train for a half-marathon. We met and talked about her new diet. She is quite intelligent and had done some digging into the LCHF world. I told her that I had little experience in this area and had never coached anyone on such a diet. Her goal was to consume fewer than 50 grams of carbs per day. How a common recommendation is that you need 100 grams per day to keep the brain functioning properly or optimally. So going to 50 is really going low carb.
So she started training under my guidance. Due to some life factors, she stopped the training after a month, but I had begun to look into the LCHF movement and it really opened my eyes. I was (and still am) skeptical that is is right for everyone.
In general I am not a fan of overly restrictive diets except where medically necessary. I believe in eating a variety of foods. My own diet is not very good so I tend not to critique the diets of others either!
I will post more on nutrition in the coming months.
Thanks for indulging me.