Why One-Size-Fits-All Diets are Inferior

“Personalized nutrition can be defined as the use of information specific to each individual, based on scientific evidence, to promote changes in eating behavior that can lead to measurable health benefits.”

There are innumerable benefits to making lifestyle improvements in the form of what we eat, how much we’re intaking, and the physical activity we do on a daily. What so many people fail to realize, however, is that this process of lifestyle change is not something that can be duplicated from person to person.

Nutrition is not a one-size-fits-all solution.

Popular dieting programs, nutrition calculators, or “health gurus” will try and convince you otherwise, but there are way too many variables at play when we go and determine what changes and/or needs must be met for a single client to see improvements.

Here are just a few factors that can differ greatly from person to person:

-Body composition (ratios of body fat to lean body mass)

-Dieting history


-Height and weight


-Current daily intake

-Physical activity level (exercise, NEAT, work/daily activity)


-Short- and long-term goals

-Mindset towards their diet/relationship with food

There’s a lot more I can list, but these are some good starting points to consider as to what makes YOU different from someone else with similar goals.

How Big of a Difference Does it Make?

To put this common misconception to the test, a 2020 study sought to determine if tailored nutrition guidance was superior in encouraging positive lifestyle and food-related behaviors when compared with generic nutrition advice (or none at all). After a nine-week baseline period in which study participants went about their usual physical activity and eating habits, researchers divided healthy men and women up into 3 separate interventions: a free-living (control) group, a generic nutrition advice (GNA) group, and a personalized nutrition advice group (PNA).

Personalized Advice vs. Generic

Subjects within the control group received no dietary advice and were instructed to go about their routine lifestyle and eating habits. Those in the generic advice group were provided with a pamphlet containing general dietary guidelines for healthy populations. This information went over 8 food groups and the respective guidelines for each.

Lastly, those in the personalized nutrition group had access to an online web portal where they received feedback based on their health parameters. Constructing of this personalized nutrition advice for PNA subjects was based on metabolic measurements taken at baseline as well as their actual food intakes (baseline habits, food frequency questionnaires), gender, age, anthropometrics, etc.

In addition to this, PNA subjects were encouraged to set a nutrition goal throughout the study period! This entailed executing their intentions as well as consulting with a dietician (3 meetings were available to them over 6 weeks). We all know the importance of goal setting, and this is a fitting feature to see within the PNA group. Not only are goals important to set, but setting intentions and formulating a plan to work towards allows those goals to be much more attainable over time, regardless of your individual circumstances. These goals can be as small as “having a serving of vegetables 2x/day,” or “having a protein source in each meal.”

1-on-1 Guidance

Personalized nutrition advice was shown to have many advantages over both the generic and control groups – one being their nutrition intake status (NIS). NIS was essentially evaluating whether the subjects’ intakes of particular food groups were sufficient (rank ranging from low to normal to excessive) in relation to guidelines.

Food intake behavior was significantly different between the PNA group and the GNA/control groups. Participants within the PNA group showed significant improvement in NIS scores compared to subjects receiving generic advice or none at all. Those provided with personalized advice were able to improve their overall diet quality and encouraged them to make less “unhealthy” choices at the same time.

While we don’t have hard numbers to go off of (carbs, protein, fats, calorie intake), it’s important to recognize the impact that implementing basic, foundational habits has on long term change. Going “0-100 is rarely successful for most. I mean, if you can do that and easily sustain it, that’s awesome; most people, however, take on way more than they can realistically handle. This often leads to burnout. Instead, inching our way towards easy and manageable lifestyle changes (such as getting more nutrient-dense foods each day or having protein in each meal) allows us to lay the foundation and set ourselves up to take on those bigger goals down the road. And do so with success!

Goal Setting

Goal setting seemed to influence the success of the participants as well (no surprise here). Of the 120 goals set by PNA subjects during the study period, only 8 of those goals were not met by the end of the intervention.

Within the PNA group exclusively, nutrition intake status improved significantly for those who had set nutrition goals compared to PNA subjects who decided not to set any specific nutrition goals. In addition to that, a massive difference was observed for the opposite in that nutrition intake status worsened significantly for subjects who didn’t set goals during the study period.

I get the appeal…

Fast results, simple instructions, restrictive meal plans, or food lists can be very tempting if you don’t know where to start. They make the process “easy” to follow with minimal thinking (or make it look that way until you actually get into it). At the end of the day, though, generic, one-size-fits-all diet advice doesn’t teach you anything about how to both sustain those changes and mold them to fit your personal lifestyle and circumstances. They don’t teach you about the diet after the diet, how to structure meals that aren’t on these programs or listed out for you, the mindset work these changes often require, and how to set intentions and execute regardless of the situation you’re in.

You can have the same goals as someone else, but the path to getting there will look very different. That’s to be expected. Recognizing that your process will be unique and not something you can compare and match to someone else’s is a hard pill to swallow for most.

Sure, it may require some extra work, but that’s what will ultimately set you apart from those who still take generic/fad diet advice. You’ll be much farther along having the right plan in place for you, your body, and your lifestyle.


Hoevenaars, F.P.M., Berendsen, C.M.M., Pasman, W.J., et al. Evaluation of food-intake behavior in a healthy population: personalized vs. one-size-fits-all. Nutrients. 2020, 12; 2819.

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