Which Diet is the Best?

Zachary Walston


Which is diet/lifestyle is better: vegan, ketogenic, or paleo? In general, neither is. For specific individuals, it depends.

There is no such thing as a one-size-fits-all diet. It doesn’t exist. There are many complexities and variables regarding the success of a dietary strategy or what is deemed a “healthy” diet.

There is no gold standard of nutrition and likely never will be due to the complexity of nutrition and our bodies. Our genetics influence our responses to a diet. Also, in attempting to maximize one goal, such as muscle gain, we may cause harm in other areas through excessive consumption of specific foods or malnutrition through a lack of variety. You have to decide what is important to you.

As a physical therapist, I think about nutrition daily. Regarding patient care, nutrition is often viewed through two lenses:

  1. What nutritional strategies can the patient use to improve their health and recovery (staying within my scope of practice regarding education and advice)?
  2. How do the patient’s current nutrition status and their current dietary habits affect the rehab plan of care?

Whether I am teaching physical therapy students in my nutrition elective at Emory University, Orthopedic Residents at PT Solutions, or patients, I always ask these two questions and expect others to do the same.

Understanding nutrition is critical for optimizing health and achieving health and fitness goals. But first, how do we know what a healthy diet consists of?

How do we measure ‘healthy’?

The volume of markers for health is staggering. Here is a sample of all the ways in which a dietary response may be deemed “healthy”:

  • General goals: weight loss, weight maintenance, hypertrophy, body fat %
  • Specific markers: cholesterol levels (HDL, LDL, TGs), c-reactive protein, resting glucose, A1C, omega-3 and omega-6 fatty acid levels
  • Hormonal control: testosterone, estrogen, cortisol, leptin, ghrelin, IGF-1, insulin
  • Vitamin/mineral levels: calcium, B12, iron, thiamin, zinc, A, C, D, K

This is not a comprehensive list, but it highlights the difficulty in defining “healthy” food. Furthermore, dietary choices can have a substantial impact on psychological health. If someone is miserable and feels their diet is a chore, not only will the adherence be poor, but it may negate potential benefits.

There is a substantial amount of evidence that supports a low carb or ketogenic diet for producing very favorable nutritional biomarkers and lipid levels. (source) There are equally favorable results for a fully plant-based, or vegan, lifestyle. (source)

My objective in writing this article is to help you make more informed dietary decisions through your own research and asking dietitians and physicians the right questions. There are many different goals to be achieved through dietary interventions and many methods to achieve them. Allow me to showcase a few.

Nutrition For Weight Loss

Whether your goals are weight loss, muscle gain, athletic performance, improved lipid profile, lower blood pressure, clearer skin, or more energy, consistent dietary habits can make or break the goals. Crash dieting is not sustainable. A meta-analysis assessed the results of 29 weight-loss studies, finding more than half of the lost weight was regained within two years, and by five years more than 80% of lost weight was regained. Dietary changes should be long-term lifestyle adaptations, not short-term band-aids.

‘Dieting’ does not mean living in a perpetual state of starvation. If you want to lose weight, you need to be in a caloric deficit. This is most effectively achieved through a combination of diet, exercise, and sleep. Your body composition goals will determine the difficulty or ease of maintaining a specific diet.

If you want to achieve and maintain a body fat percentage under 8%, you often will need to be in a hypo-caloric state which can lead to the chronically altered secretion of testosterone, cortisol, leptin, and ghrelin (similar to sleep deprivation). (source) These hormonal alterations are detrimental to your ability to heal from injury and can worsen your mood.

If you have difficulty with caloric control, intermittent fasting, or time-restricted feeding may be a great option for you, as the research demonstrates it may improve satiety leading to fewer calories consumed. (source) Research shows additional benefits of fasting including optimizing physiological function, enhance performance, and slow aging and disease processes. (source, must-read)

Nutrition For Building Muscle

If your goal is to maximize muscle hypertrophy (building muscle), the protein demands will be higher than strictly necessary for optimal health. While consuming high volumes of protein can be more difficult to achieve with a plant-based or vegan diet, the amount of protein consumed in the paleo diet is often excessive.

Studies demonstrate that we maximize our therapeutic effect from protein around 1.7–2.2 g/kg of body weight. (source) Evidence suggests excessive protein intake may worsen insulin sensitivity and lead to insulin resistance. (source) More is not always better.

Be Cautious When Reading Nutrition Research

By no means am I covering all the different dietary approaches or nuances of dietary intervention. I use plant-based, ketogenic, intermittent fasting, and paleo as they are commonly adopted and I have experimented with each personally. My intention is to highlight how each can effectively be used and each brings its own set of considerations.

Again, there is no gold-standard or one-size-fits-all best diet.

Tunnel vision can be dangerous in the world of nutrition, especially when it is combined with confirmation bias and epidemiologic research. For example, several large prospective cohorts, including the China Study, have drawn have concluded animal sources (specifically red and processed meat) of food increase the incidence of heart disease and cancer. (source, source, source)

The primary issue is isolating red and processed meat as the sole causes of negative health effects. Further analysis revealed the following were associated with increased red & processed meat consumption:

  • Decreased exercise frequency and duration
  • Increased Body Mass Index (BMI)
  • Increased smoking
  • Increased prevalence of diabetes
  • Lower (not a typo) cholesterol levels
  • Increased total caloric intake
  • Increased alcohol intake

This leads to a couple of questions. Is it possible that the elevated BMI, diabetes, low levels of cholesterol (we need cholesterol), or a combination caused the increased mortality rates and not the red meat?

It is very possible the red meat caused the development of those conditions; however, an association is not a cause and effect relationship. Furthermore, is it possible the poor exercise habits, smoking, increased caloric intake, increased alcohol intake or some combination caused the increased mortality rates? Perhaps they even caused elevated BMI, diabetes, and low levels of cholesterol alone.

We must consider all that is potentially consumed with the meat (the buns, the fries, the sodas, the sauces, etc.), the source of the meat (wild-caught, foraging, grass-fed), and the cooking methodology (low vs. high heat, fried, baked, etc.). Lastly, we can layer on additional lifestyle habits, such as sleep and stress levels.

I am not saying to consume pounds or red and processed meat daily. Based on the available research, I would categorize processed meat as net ‘unhealthy’ and red meat somewhere in the middle. A lot depends on the individual and the amount of wiggle room they have available. If you are on-point with your diet, do not have heart conditions or diabetes, and regular exercise, then enjoy the steak. If you have high blood pressure and a BMI north of 30, that steak will likely be more harmful. Not a guarantee by any stretch, it is all about risk management and looking at the big picture.

Let’s flip the script and look at sugar. A vegan diet will be naturally high in fruits and vegetables. What happens if I focus on the sugar components? Sugar consumption is linked to the same dramatic rise in obesity, cancer, and heart disease, in addition to Alzheimer’s disease. (source)

Consumption of fructose, which is the sugar found in fruit and fruit juice, may be of greater concern due to its linkage to visceral adiposity (i.e. fatty liver disease) and hypertension in rodent studies. (source) The “natural” part of sugar does not make it healthy; sugar is sugar. I have no issue with remaining strict in a diet; but does this mean we should avoid sugars at all costs? A proponent of a ketogenic diet may propose such a strategy.

Sugar, and fructose specifically, is the root of all evil. Our body uses sugar (glucose) for energy, especially in the brain. While we can run on ketones (ketogenic diet) we do not know the long-term effects of running exclusively on ketones. Additionally, fruits and vegetables contain a lot more than sugar.

The big advantage of plant-based foods is everything outside the macronutrients (protein, fat, carbohydrates). The fiber, vitamins, and phytochemicals all help with body functions, immunity, inflammation control, and cell repair. (source) Focusing on a single nutrient, especially a macronutrient, ignores all the other health benefits of a food.

It is difficult to encompass all possible benefits of a diet within a specific dietary approach. The specific goals you are trying to obtain along with the pros and cons of each dietary choice should be weighed.

So Which Diet is Best?

At this point, I hope the answer is clear: it depends.

There is a lot to consider when designing your dietary strategy. Aside from the basics, you need to layer in activity level, stress, cognitive demands, and culture. No two people will respond the same to dietary strategies. This is where tracking comes into play.

I encourage you to track your own dietary strategies — specifically write them down — and how they affect your mood, sleep, and physical and mental performance. If you are seeking a dramatic change in your diet, consult your physician, and get blood work. Even the simple act of tracking is a powerful exercise to gain a better understanding of your dietary strategies, your motivations behind food choices — taste, performance, weight, culture, cost, ease to cook or obtain — and your understanding of the impact food has on your lifestyle.

If you want to learn more about nutrition, the data is out there, but you need to understand the limitations of nutrition research. Go to the source, not the popular press articles with catchy headlines such as “Bacon kills” or “Never Eat These Seven Foods.” Most popular press articles draw incorrect and oversimplified conclusions. Much of the nutrition research is riddled with limitations and conflicts of interest.

I understand this can be disconcerting, and what I am suggesting requires more effort, but it will be worth it. Consult with a registered dietician to get on the path if you don’t know where to begin. Otherwise, experiment, track your results, take a comprehensive approach, and read.

We are unable to develop a one-size-fits-all diet that checks all the boxes for optimizing “health”. But we are able to design personalized dietary approaches with a little bit of effort.

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I am a physical therapist, researcher, and educator whose mission is to challenge health misinformation. You will find articles about health, fitness, medical care, psychology, and professional development on my site. As the husband of a real estate agent, you will also find real estate and housing tips.

Atlanta, GA

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