Why one-size-fits-all diets don’t work

Low-carb, ketogenic, low-fat, high/low-whatever is really just hype.

Billions of research dollars are spent trying to understand why people are overfat, but if you’re among the sheep the herd is headed for the cliff.

Whenever a researcher gets close to showing how certain dietary components influence insulin and its effects on body fat stores, the publishing game is to state that “more research is needed.” In other words, “we’re not sure yet so give us more research money.”

This can be great ammunition for junk food companies that claim there is no research to confirm sugar is unhealthy, and keeps politicians from implementing useful policies directed at improving the health of their constituents (especially considering that Big Sugar lobbies overshadow them).

Since most people are strongly influenced by recommendations in the media and those promoted by governmental agencies regarding their health, it’s no surprise that the general population continues to be more overfat and unhealthy. However, those individuals willing to take charge of their own health can break from the herd and enjoy the benefits of wellness and reducing excess body fat.

As is well known, insulin is strongly associated with body fat — too much production of the former can contribute to the latter. Other associated secondary problems include chronic diseases such as type 2 diabetes, cancer, cardiovascular diseases, and many others.

The pharmaceutical industry knows the research. Drugs that reduce insulin also reduce body fat. But this is not an answer as lifestyle changes can do the same, only better — you just have to know which eating pattern works for your body’s fat-burning needs. Obviously, drugs come with side-effects, are expensive, and don’t address the cause of the problem — eating junk food.

Lifestyle factors that promote increased insulin and body fat are numerous. They include genetics, the number of beta-cells in the pancreas and other factors we have little or no control over. Diet is the most influential lifestyle factor. While micronutrients such as vitamins, minerals and phytonutrients can affect the insulin-body fat process,  macronutrients — fat, protein and carbohydrates — are the most powerful influence.

Fat: Dietary fat can sometimes, in some individuals, increase insulin, but this occurs more often in the presence of carbohydrate. A diet too high in fat and carbohydrate may be the most common way millions of people eat, and certainly a reason why up to 76 percent of the world’s population is overfat. Eating only natural fats and natural carbohydrates is key.

Protein: Dietary protein can increase insulin stimulation too, and in this case can increase fat storage as well. The most influential amino acids in this regard are arginine, and the so-called branched-chain amino acids — isoleucine, leucine, valine, tyrosine and phenylalanine. Eating moderate amounts of concentrated protein foods work best, choosing from eggs, dairy and meats.

Carbohydrate: Whether in combination with fat and or protein, carbohydrate foods are the most powerful stimulator of insulin and contributor to increased body fat. In particular, refined carbohydrates are most potent due to their glycemic influence. Avoiding junk food in all its disguises remains rule No. 1 not only if you want to reduce excess body fat but for overall improved health and fitness.

There are plenty of studies that demonstrate how fat, protein and carbohydrate influence insulin, body-fat storage and poor health. There are even more on the carb-insulin issue. These usually have cautious results that often appear conflicting because there is clearly considerable variability in the relative responses to these foods between individuals. Yes, we all respond a bit differently to food. Unfortunately, no study has simultaneously compared the responsiveness to dietary fat, protein and carbohydrate.

Because carbohydrates are the most powerful lifestyle factor influencing insulin to raise body fat storage, it’s the best place to start to make healthy changes for most people. It’s why the Two Week Test was developed. It’s your very own research, a study of one — you.

Our variability in response to food is one of the unique human features we each possess as individuals. A recent scientific review by Nicole Templeman and colleagues (the Journal of Endocrinology) states that, “Genetic profiling studies could be used to understand the mechanistic underpinnings of this variation [individual responses to macronutrients]. Answering this question could usher in a new era of nutrigenomics to minimize obesity and diabetes risk.”

But wait. Don’t the most intelligent individuals already do this? In addition, some clinicians have been helping individuals discover their specific dietary needs for decades, without a one-size-fits-all diet.

Individualization is the only real proof in human health studies. While usually taken as an excuse why things may not work for everyone — a study of one — the scientific approach of looking for the answer really means looking for that one size that fits all, and when it’s not found it leads to the notion that “more research is needed.” Each of us already possesses this unique ability to find what works best for our individual needs.


  • Mark Davis says:

    After following Phil’s advice for over 20 years on diet I can advocate his common sense approach.

    I formulated his advice into these easy to follow everyday principles to keep it real. I hope I have it right and may be useful for others to get a grip on it:

    Everyday I aim to consume:

    Adequate water for my size climate and activity levels.
    5 handfuls or more of 10 or more variety of vegetable and fruits.
    Protein is the star of every meal or snack. 3 or more servings a day.
    Balance small quantities of natural fats including egg yolk, avocado, nuts, seeds, coconuts and olive oil ensuring to include the omega 3 variety (fish, walnuts, ground flax, greens) – I don’t do supplements personally so no EPA fish oil for me.
    Add some unrefined sea salt to most my meals.
    Use spices and herbs where possible.

    Outside of that I occasionally treat myself when in social situations, so in fact I don’t miss out on anything at all. Works a treat.

    I never did the two week test but Phil did teach me how to use food for performance, health and most importantly my longevity. As a fitness professional I have advised others to use the two-week test and they have had great success doing so.

    I advise people to grow young we need to grow up, and make mostly mature decisions about our food choices. Its easy with the above approach I reckon.

    Hope this helps.

    Bon Appetite!

  • Samuel Christensen says:

    Hi everyone, I have to say I definitely subscribe all of the info brought by Dr Phil Maffetone. I have been trying all sorts of diets, vegetarian, raw food, Mediterranean diet, Paleo and Keto and what I have learned thru all thoses years is that you have most of those the answer In you. Trying to listen to your body and his needs is everything. Absolutely, veggies are kings and you have to stick to them every day;) grains or food with high glycemic impact you have to figure out your own consumption, if you cut too much you have consequences! As the same for fat, if you eat too much you are also going to experience consequences. You need balance and I believe that’s the part no one has been talking about! All the food guru’s bring you one efective and only solution, but that isn’t entirely true! We live in a world of excess and we are just exceeding on what we believe is closer to us and that in most of the time is food.

  • Matt K says:

    For those who wish to eat a plant-based vegan diet for ethical reasons. Is a diet of vegetables, fruits, nuts, beans, and intact whole grains with D and B12 supplementation good enough? By eating those foods, one could get a decent balance of carbohydrates, fat (especially from the nuts), and protein and refined carbohydrates could still be avoided.

    I also wonder how much improved athletic performance because of a cleaner diet is attributable to the meat and how much is connected to vegetable consumption. Usually, when people go low-carb or start eating healthier, they start to eat more vegetables which most Americans hardly ever get enough of…


    • Matt:

      The vegetable consumption is absolutely critical to health and fitness, due to the array of vitamins, minerals, phytonutrients, enzymes, etc. as well as the fiber content. However, what meats and animal proteins bring to the table are an array of fat-soluble vitamins that are not easily found in many plant foods. While it is entirely possible to get all the nutrients you need from a vegan diet, that requires far and away more nutritional sophistication than to get the entirety of the nutrients you need from a plant-heavy but omnivorous diet.

  • Joe says:

    “Eating moderate amounts of concentrated protein foods work best”

    Would you mind giving some guidelines/rules of thumb to quantify a moderate amount of protein intake? Both for a regular day and after a fairly intense/long workout (say a 3H bike ride, or a 10K run). I typically increase my protein intake 2x to 3x for the meal after a strenuous exercise, thinking/hoping it will help with the adaptation process and increase future fitness. But now you have me slightly worried…

    Thanks a lot for your wealth of advice and material, I have found your articles and podcast very enlightening.

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