This is the time of year where we commit to get healthier by exercising more and eating better. But what does that mean?

It turns out that it can mean different things to different people, according to a November 2015 study published in the journal, Cell. Israeli researchers tracked the blood sugar of 800 people over a week and found when they ate the same meals it was metabolized differently from one person to another. It wasn’t just blood sugar that helped the researchers come to this conclusion. Data was also collected through health questionnaires, body measurements, blood tests, glucose monitoring, stool samples, and an app used to report lifestyle and food intake (a total of 46,898 meals were measured). In addition, the volunteers received a few identical meals for their breakfasts.

What they found is: Different people show vastly different responses to the same food. “Measuring such a large cohort without any prejudice really enlightened us on how inaccurate we all were about one of the most basic concepts of our existence, which is what we eat and how we integrate nutrition into our daily life”, said Eran Elinav of the Weizmann Institute of Science in Israel, in a prepared statement. “In contrast to our current practices, tailoring diets to the individual may allow us to utilize nutrition as means of controlling elevated blood sugar levels and its associated medical conditions.”

Basically, this is the reason why your best friend’s diet may not work for you. And it isn’t just diet, when it comes to food, our genes, how our food is produced — growing and processing, and when it is consumed, all affect how our bodies interact with food. So despite the numerous articles that tout eating foods to protect yourself from breast cancer, heart disease, or possibly improve gut health (I have written many of these articles), whether eating these foods will give you the desired outcome is possible but the probability is still questionable.

That’s because nutrition science is tricky — experimental groups are difficult to control, it is hard to know if it is the food that is being tested or hypothesized about or whatever else the subjects are eating or doing in their life. (For a better explanation of the issues with nutrition research, see this New York Times article.) Trying to eat from the headlines will drive you crazy.

All these articles and testimonials should be seen as what they are — suggestions. This can be maddening if you are looking for a way to learn how and what you should eat to feel good. Weight loss is secondary, because if you can figure out how you should eat to feel great everything else should fall in line: weight, mood, energy, etc.

The Diets You Should Consider Trying This Year

If you haven’t read Mark Bittman’s In Defense of Food, do. He discusses the politics, policies, and research surrounding food and how it drives us to talk about food (“as nutritents”) and how we eat it. His “Eat food. Not too much. Mostly plants.” is explained simply, and if you’re looking just for a how-to guide, start with section III. (Or pick up, Food Rules: An Eater’s Manual)

Then, if you do that and you still don’t feel fantastic, it’s time to dial into how your body reacts to food, and pinpointing that food. The best way to do that is with an elimination diet. For this, I suggest The Whole 30 because it gives you set rules and takes how food is processed in its design. It is highly restrictive for the 30 days, but at the end you will know what foods make you feel great and which ones don’t.

By using these two tools, figuring out the best way to eat for you should be a little easier. It has for me. I know that I feel better (i.e., my mood is better; I have less pains; and my thinking is clearer) when there isn’t bread, sugar, or dairy in my diet. It doesn’t mean I always eat this way but I at least know how I should be eating. And that’s the subject for another post.