“Big” Vegan, and Finding the Real “Game Changer” for Your Endurance Performance

Jan 09, 2020

- Professor Grant Schofield and Dr Daniel Plews 


We’ve watched  the battleground in diet shift recently from debates around saturated fat, and eating more healthy whole grains, to a largely vegan agenda. The ideology of the Garden of Eden diet, is close to the vegan ideals driven primarily through the Seventh Day Adventist Church, and touted as a recruitment strategy (or “health ministry”). Recently, it's gone to greater levels. The Netflix doco “Game Changers” has seen widespread discussion around this topic, and we’ve been fielding a lot of questions around this of late. This blog is our attempt to sum up our thoughts.

We’ve listed the pros, neutrals, and cons of adopting such a diet for general health and when in the context of sports performance. There are many ways that you can approach this topic, from health, sustainability, moral and personal perspectives to a sports performance perspective. We'll be tackling a few different perspectives that we consider important to consider when discussing this topic.

Pros for going vegan:

  1. You might clean up your diet as part of the process and eat less processed food, and be in less caloric overload. Therefore you will be less inflamed, leaner, and less prone to injury than before. This is great, but doesn’t test the hypothesis that meat or animal products inhibit athletic performance.
  2. According to animal studies, being in a constant caloric deficit could extend your life. However, low energy availability for athletes will lead to RED-S (Relative Energy Deficiency in Sports) and result in impaired immunity, bone health, metabolic rate, menstrual function, protein synthesis and cardiovascular health (1).
  3. Getting too much iron causes insulin resistance, the decreased amount of iron you'll be absorbing going from an omnivorous diet to a plant-based diet could therefore decrease this.
  4. For the insulin resistant, adding extra (animal?) fat may exacerbate an already high glycaemic and insulin response in comparison to the same amount of carbohydrate.
  5. Red and white meat compared to plant protein may lead to an inferior lipid profile (see Ron Krauss’s feeding study)(2).

Neutral or unresolvable in the debate:

First, it’s impossible to unpack cause and effect from prospective epidemiology and cross-sectional studies in this area because the idea of eating less animal fat in particular has been an ingrained public health message for decades. On the same basis, we won’t claim that the higher observed incidence of depression and anxiety for vegetarians and vegans in some epidemiological studies is causal (see here for a review of the recent research).  Or that the fact that the Seventh Day Adventist men who have the lowest sperm count or motility are the vegan ones (3). All of these studies are impossibly confounded. You can’t have it both ways, so we will ignore both sides. The much-touted China study of course falls into this category, especially when you consider the confounding of Hepatitis which is well known as a serious shortcoming of the China study (see Denise Minger’s discussion and re-analysis of the China study (4). This is a seriously interesting read if you want to get into the nitty-gritty of the truth vs fiction in epidemiology and veganism).

We’re unaware of any study which has tested the hypothesis that the exact same nutrients in the diet, one from animal and plant products, the other from exclusively plant products, have superior outcomes one way or another.  

It’s almost certain that humans evolved in an omnivorous environment. We are morphologically omnivorous. Despite, false science in movies like the Game Changers, our colon and general design is omnivorous, not herbivorous. There is a theory that the energy density from animals provided part of the causal chain in humans developing a brain size which can survive its own high energy demand with low food security (i.e. starvation sometimes). Humans are very good fat burners, endurance runners, and “fat storers”, compared to other animals. It is likely that the well-developed ketogenic system humans enjoy is part of this evolutionary legacy. That said, who knows exactly how ancient humans lived and what they ate exactly (or what the variation in these diets were), and furthermore, does this in any way mean what they did was optimal? 

There is a claim that animal farming is a major cause of climate change. We’re certainly not experts in this field. It’s hard to unpack all of this, but here’s our lay view:

  1. The major ecological problem is that there are too many humans on the planet, and there are even more coming as we are in an exponential phase of population growth. We have no idea how to solve this, but it is the elephant in the room.
  2. The increase in population is creating lots of problems including mass extinctions of other animals, deforestation, pollution, and a warming planet. Taken together this is the major problem of our times. Decreasing the rate of population growth would be a good start.
  3. When you look at the way we mass farm some animals and animal products, it is abhorrent. One of our colleagues worked in a battery hen farm once. They said it was terrible. We can’t tolerate those methods and must do better.
  4. Much of the arable farming land (up to 70% we hear?) is not suitable for crop growing. So a well-formulated farming plants where ruminants are part of the carbon capture cycle with grass seems feasible as carbon neutral, or even could remove carbon.
  5. The data on the emissions the agricultural and farming sector makes are in the order of 6-12%. At least half of this is probably due to cropping. The big target isn’t farming and agriculture, it’s transport and energy. That’s not to say we can’t do better.


A classic poor outcome from a well-meaning climate change agenda is that the NZ government recently agreed to remove meat and dairy from NZ hospitals for climate reasons.

There is a claim that meat and animal products cause inflammation. Correct, of course they do – they activate the anabolic (building) response through insulin and mTOR pathways (5). Inflammation is critical to growth and building. Cell division and growth is an inflammatory process. It’s chronic inflammation that’s the issue, and we’re not aware of how meat and animal products meaningfully contribute to this in the context of a whole food diet. Randomised trials of such diets show no evidence of chronic inflammation, in fact they resolve this (See David Ludwig’s recent review on low carb high-fat diets (6)). We’ll talk more about the anabolic/catabolic system later.


Cons for going vegan:

  1. You will almost certainly be deficient in various essential nutrients. Some of these are iron, calcium, copper, DHEA essential fatty acids, folate, and vitamin B12. Although these nutrients are plausibly in some plant materials they are much less bioavailable, and/or you’ll need to find specialist products which are essentially supplements, such as eating loads of seaweed. We contend that without serious supplementation, and/or special foods which amount to supplementation, humans cannot thrive without the essential nutrients in animal products. This is a big deal if you are committed to eating whole, real food.
  2. It’s really useful to have metabolic flexibility. A healthy functioning human should be able to access and use the anabolic system and the catabolic system. It’s our contention that much of the metabolic syndrome-related problems we have are due to a lack of metabolic flexibility. Some notes on all of these below:
    1. Anabolic
      The anabolic state is a growth state where cells are dividing. Anabolic processes are driven primarily by insulin and the accompanying biochemistry. Obviously you need growth so being in this anabolic state sometimes is good, but all the time is bad.
      • Driven by dietary carbohydrate, and a lesser extent by protein
      • MTOR activation
      • Inflammation
      • Cell division
      • Growth
    2. Catabolic
      The catabolic state is the opposite of the anabolic state. It’s a non-growth/repair state. The body stops cell division and concentrates on tidying up cells, repairing any damaged genes, and killing off any cells that are past their “use by date”.
      • Driven by the presence of ketones (low carb, fasting)
      • Non-growth
      • AMPK signalling
      • Autophagy and cell repair
      • Anti-inflammatory
      • Endogenous anti-oxidants produced


Metabolic flexibility – The ONE big idea to understand

Humans are designed to be metabolically flexible (also called being “fat adapted”). That is to say, if you want the best out of your brain and body, then you should be able to rely on fuel from both carbohydrates and fats, as, and when, you need them. Someone who is metabolically flexible can use fat as the primary (and almost exclusive) fuel when they are resting, sleeping, and moving around at a fairly slow pace. As they start to move around at a faster pace – like fast running – then they will be able to take advantage of extra fuel supply from carbohydrate, and when they are going nearly flat out, they will rely almost exclusively on carbs for fuel. This is exactly what we teach in our course LDT 101: The Practical Application of Low Carbohydrate Performance for Long Distance Triathlon. Studies have shown that having a high fat oxidation (and thereby being metabolically flexible), has positive implications on long distance triathlon performance (i.e. the more metabolically flexible you are, the better your long-distance triathlon performance (7).

We measure metabolic flexibility in our lab using online gas analysis. Dan goes through this in greater detail in Endure IQ LDT101, but in brief we measure the proportion of inhaled and exhaled oxygen and carbon dioxide to understand just how much fat and how much carbohydrate someone is using from rest to flat out exercise. What you want to see during this test is in Figure 1 - that is this athlete mostly uses fat for fuel at low running speeds, through to mostly carbs at faster speeds. This athlete is a male triathlete who has been using the low-carb, healthy-fat approach for over two years. He is highly metabolically flexible.


Figure 1: Calories per hour derived from carbs (red) and fat (yellow) [vertical axis] for a metabolic efficiency test – treadmill-running speed (min per km) [horizontal axis] using respiratory exchange. The athlete is a 39-year-old male elite triathlete who has been LCHF for at least two years.


Other athletes we’ve tested aren’t as good at using fat as this athlete. Here’s another test, however this time the athlete is metabolically inefficient (Figure 2). This woman is a pretty good age group triathlete, but she is really not able to access her body fat stores as a fuel source at any exercise intensity.

Figure 2: A metabolically inflexible athlete. This is a high-carb eating high-level age group female triathlete.


These two athletes are bread and cheese. One can easily access their body fat stores as a primary fuel at low exercise intensity. He can provide energy from fat right up to very high exercise intensity. He is a fat-burning machine who can access the tens of thousands of calories of fat he has stored around his body. He can maintain a healthy lean body weight easily and doesn’t have to eat sugar and carbs every time he goes training.

The other has to rely on the very limited carbohydrate supply (maybe 2-2500 kcal) she has stored in her muscles and liver. She has to eat extra sugar every time she trains, and fuel up again afterwards. She’s tired and has trouble getting her weight down to race.

Being a fat burner has obvious advantages in some sports, like endurance events where having enough fuel to make the distance is an issue. This includes long-distance running, triathlons, cycling and anything else where you are training, racing or competing for a few hours or more. You have access to a big fuel tank (fat) and can spare the small tank that provides extra power when you need it (carbs). In other words, you can go faster for longer.

But it doesn’t stop there. The fat burner has the potential for significant health and performance advantages in any sport where weight, cognitive performance, fuel, and high training and competition loads are a factor. This includes weight class sports, all day sports like sailing, and team sports.


Vegan and fat-adapted? An impossible mission.

A diet which is based on whole foods from plants and animals is naturally lower in carbohydrate, moderate in protein and higher in fat. Such a diet provides good outcomes for all the major metabolic measures of interest – it’s anti-inflammatory, and reduces all of the parameters of metabolic syndrome. Such a diet can allow an athlete to access fat as a primary fuel source – because fat is burning cleanly without the reactive oxygen species of carb-burning meaning the chances of prolonged low-intensity endurance exercise creating chronic inflammation are reduced. 

Importantly having the catabolic (fat burning) system intact and fully functioning doesn’t impair the ability of the anabolic (carb-burning) system functioning at higher intensity exercise (8), it just means you get the best of both worlds. You can augment your fuel with carbs you eat and get the benefit, and be twice as good at the overall load of accessing fat for energy at lower intensities. Why would you avoid that?

And all this has virtually nothing to do with avoiding animal products, especially meat. In our opinion, well-raised animal products are convenient, whole and nutritionally complete food sources for humans, especially those wanting to avoid supplementation and stay lower in carbs and therefore be metabolically flexible. Getting some, or even most of your protein from healthy animal sources is going to mean you can also get a range of healthy fats, keep the carbs down, and expose yourself to the range of essential nutrients necessary for human health and performance.

You can go vegan if you want, that’s fine. Just be aware of the nutritional (deficiency) risks, and be aware that it’s going to be harder to get low enough in carbs to be fat adapted. It’s possible to eat well enough on a plant-only diet, but it is likely very difficult. For almost everyone, including us and the many athletes much better than us, they manage their diet for peak performance by being whole-food omnivores. The vast majority of elite athletes eat this way. That doesn’t prove the point, in the same way “Game Changers” doesn’t prove the point. 

The point is that, in our opinion,  omnivorous fat-adapted humans are at a performance advantage from firstly, their advantageous effect on metabolic flexibility and secondly, nutrient availability. Reducing animal protein means you reduce the amount of fat in the diet, and then to satiate yourself you typically eat more CHO, making it almost impossible for an athlete to meet daily calorie requirements whilst keeping carbs low with a restrictive diet. 

The vegan/not debate is essentially an unwinnable argument. To us, people will see the world the way they want to. The fact that L. Ron Hubbard could found and run the Church of Scientology is evidence enough that people can believe anything and defend it until the end of the earth.

Of course, therefore I can’t be excluded from that either. We’ll leave that judgement up to you. :)

Grant and Dan




  1. https://blogs.bmj.com/bjsm/2018/05/30/2018-update-relative-energy-deficiency-in-sport-red-s/
  2. Bergeron N, Chiu S, Williams S, King S, Krauss R. Effects of red meat, white meat, and nonmeat protein sources on atherogenic lipoprotein measures in the context of low compared with high saturated fat intake: a randomized controlled trial. The American Journal of Clinical Nutrition 110: 24-33, 2019
  3. Orzylowska E, Jacobson J, Ko E, Corselli J, Chan P. Decreased sperm concentration and motility in a subpopulation of vegetarian males at a designated blue zone geographic region. American Society for Reproductive Medicine 102: 273, 2014
  4. https://deniseminger.com/the-china-study/
  5. Detzel C, Fleming M, Weaver E. Functional animal proteins activate mTOR and bind pro-inflammatory compounds. Journal of the International Society of Sports Nutrition 12: 35, 2015
  6. Ludwig D. The Ketogenic Diet: Evidence for Optimism but High-Quality Research Needed. The Journal of Nutrition: 1-6, 2019
  7. Frandsen J, Vest SD, Larsen S, Dela F, Helge J. Maximal Fat Oxidation is Related to Performance in an Ironman Triathlon. Int J Sports Med 38: 975-982, 2017
  8. Dostal T, Plews D, Hofmann P, Laursen P, Cipryan L. Effects of a 12-Week Very-Low Carbohydrate High-Fat Diet on Maximal Aerobic Capacity, High-Intensity Intermittent Exercise, and Cardiac Autonomic Regulation: Non-randomized Parallel-Group Study. Front. Physiol 10: 912, 2019 


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