It’s been almost five years since I ran my first 30-day vegetarian experiment, with the primary aim of seeing how the diet would affect my training performance and body composition. I was motivated in part by genuine curiosity and in part by ethical considerations. I wanted to reduce my meat consumption—an industry widely known to be cruel toward animals and damaging to the environment, contributing to greenhouse gas emissions, water pollution, and climate change.
At the time, I was also naïve, believing I would experience nutrient deficiencies and declines in endurance and strength performance. I wanted to see if that was really the case.
From a performance perspective, I actually felt more energetic in my workouts, and by ensuring I was getting adequate calories and protein from complete amino acid sources, I did see some muscle growth from when I started the challenge in February 2021 through March (progress photos below):
While I returned to eating meat after the 30-day period, my intake significantly decreased from two to three servings per day to one, with many meatless day (a roughly 80% reduction).
Since then, I haven’t been a big meat eater. If I do eat it, it’s usually fish or chicken, rarely beef, and almost never pork. However, over time, I developed a nagging guilt whenever I ate meat. Educating myself on the meat industry and its environmental impact made the act of scanning a chicken breast at the grocery store feel morally wrong. It’s a familiar feeling when I was in the throes of a drinking problem, buying those tall cans of IPAs from the liquor store, knowing that this was a really bad idea. That’s cognitive dissonance for ya: knowing that the thing we believe provides pleasure often delivers disproportionate levels of pain.
Lasting change rarely comes from being told what to do. It comes when our actions no longer align with the person we want to be. Sometimes we reach a breaking point, but oftentimes, it’s the people in our lives that directly or indirectly influence our actions.
My partner, McKenzie, is vegetarian, and naturally, over the course of our relationship, we’ve eaten more vegetarian and vegan meals together. Ground turkey was replaced with Beyond Meat, chicken breast became tofu, and I’ve been really enjoying it. We tried new vegan and vegetarian restaurants together, new recipes, and got creative when travelling together. Then, during one of our date nights at an amazing vegan restaurant in Vancouver, I got the idea to do another 30 day vegetarian challenge. So, I started the very next day.
I went 60 days vegetarian, then had some fish, and went right back to it. It’s now been over 60 days since I’ve eaten land animals, and I plan to keep rolling with it. I don’t love labels, and I don’t love rigidity, so for now, I’m choosing to eat vegetarian most of the time.
This post highlights my experience with an emphasis on the training aspect, what the science says (and doesn’t say), and finishes with a full day of eating with macro and calorie counts included. But first a quick disclaimer: I’m not a registered dietitian nor pretend to be one. I’ve linked studies where relevant, but encourage you to check them out, and scrutinize them for yourself. DIY is the best way to find out what works for you. It’s always a good idea to check-in with a medical professional or consult with a registered dietitian. Let’s dive in.
But first, a fun fact…
Did you know there are at least eight different types of vegetarian diets?
*I had no idea an ovo-vegetarian eats eggs but not meat. I’ve also never heard of a pesco-lacto-ovo-vegetarian, but I guess that’s me. If you fall into any of these long-tail categories, you may have just found a new conversation starter at your next party.
Now back to your regular programming…
Does Vegetarianism Impact Endurance Performance?
First off, hi! I’m Emily and I’m an ultrarunner. Right now, I’m in my off season. I lift weights five days per week, run casually four to five days per week, and hike once per week. Anecdotally, I haven’t noticed major changes in my endurance eating vegetarian, but I’ve also been traveling, was sick for 10 days, and am undergoing an egg-freezing cycle—way too many variables to draw conclusions from.
So, let’s turn to the science instead.
I was surprised to learn that while there is an abundance of research on how nutrition impacts endurance and strength performance, there is very little comparing vegetarian and vegan diets vs. an omnivore diet from a training perspective. One meta-analysis looked at papers from 1999-2021, and the researchers were only able to use 14 studies for analysis. The findings I present to you are from those 14 studies. In short, the research suggested that vegans and vegetarians may be at an advantage from an endurance perspective, but may be at a disadvantage for strength.
Let’s tackle the endurance point first.
Does Vegetarianism Impact Endurance Performance?
A common measure of endurance performance is VO₂max, or how efficiently your body utilizes oxygen during intense exercise. When we’re working out at intensities above ~60% of VO₂max, our primary energy source is from carbs. Longer bouts of effort at lower intensities depend more on fat oxidation.
Vegan and vegetarian diets, according to one study, consumed around 16-17% more carbohydrates than their omnivore counterparts, giving them a slightly greater edge in higher intensity efforts. The study also showed that vegans have lower fat and protein intakes than omnivores, and tend to consume less saturated fat, providing more cardiovascular benefits.
But that’s not the only thing that matters.
Other factors like the number of mitochondria in your muscles and the density of tiny blood vessels (capillaries) that deliver oxygen to muscle also influence performance. Studies to date haven’t found meaningful differences in mitochondrial content between vegans and omnivores, though some research suggests vegans may have slightly higher mitochondrial DNA, but the functional difference is unclear.
One study discussed a soy compound—which vegans typically consume more of—that may reduce the growth of new blood vessels. However an important caveat is that this hasn’t been well-tested in a training setting.
A 2021 study examined 16 young omnivorous men and 9 vegans, assessing relative and absolute VO₂max on a cycle ergometer. The data showed no differences in cardiovascular fitness, suggesting that vegetarian and vegan diets in the long term don’t have negative effects on endurance performance, particularly higher-intensity exercise where carbohydrate availability matters.
There was a lot of “maybe,” “kind of,” “we think”, but little that’s definitive. Most studies didn’t conclude that vegan or vegetarian diets are superior to omnivorous diets, but some detected a tendency toward improved aerobic performance, indicating that more research is needed.
Vitamin Deficiencies
The analysis also observed that meat-eating and vegan diets showed the biggest differences in macro intake and potential micronutrient deficiencies. Researchers pointed out that people following vegetarian and vegan diets may consume less vitamin D, B12, and iron.
Iron is important for athletes in maintaining healthy hemoglobin levels. While you can get iron from plant sources (non-heme iron), it’s generally absorbed less efficiently than iron from animal sources (heme iron). A simple fix can be supplementation when appropriate and regular bloodwork to monitor deficiencies, especially if you’re a more serious endurance athlete.
In sum: as long as you’re getting enough calories, the right macronutrient mix for your sport, and supplementing as needed, it likely doesn’t matter whether you’re omnivorous, vegan, vegetarian, or pesco-lacto-ovo-vegetarian. Working with a dietitian to determine your individual needs is always a good idea.
Does Vegetarianism Impact Strength Performance?
The meta-analysis reported that vegetarianism may be at a disadvantage for strength for the following reasons:
1) Lower creatine levels
Strength performance is highly dependent on the availability of phosphagens, primarily ATP and phosphocreatine, which provide rapid energy for short-duration, high-intensity efforts such as resistance training and power movements. During activities like powerlifting, 1RM strength work, and explosive movements, energy is supplied predominantly by the ATP–phosphocreatine system and relies heavily on type II (fast-twitch) muscle fibers.
The best dietary sources of creatine are animal products such as red meat, fish, poultry, and pork. Because vegetarians and especially vegans consume little to no dietary creatine, they tend to have lower blood and muscle creatine stores than omnivores, which may modestly reduce maximal power output and strength potential. In contrast, lower creatine availability has minimal impact on muscular endurance or higher-repetition hypertrophy-focused training.
A simple solution for vegetarians and vegans is creatine supplementation, which is one of the most extensively studied supplements on the market and has consistently been shown to increase muscle creatine stores and improve strength and power performance.
2) Protein
One of the most timeworn arguments that I can almost guarantee all vegetarians and vegans get annoyed by is the protein question: If you’re not eating meat, how do you get your protein?
Protein is a building block for muscle growth and a key player in strength performance. With hard resistance training (over 70% 1RM), muscle protein synthesis (MPS)—a process that helps repair muscle damage from exercise—increases several-fold above our baseline.
Both MPS and muscle protein breakdown (MPB) increase after resistance training, and the net result can be a temporary deficit in muscle protein balance. Your body then uses dietary amino acids to repair and rebuild the damage done in training. Consuming adequate protein helps shift that balance toward recovery, repair, and adaptation. Persistent under consumption of protein, especially when we’re training hard can impair recovery and progress.
While studies differ on nutrition timing and the exact quantity of protein needed, many suggest 20–30g of high-quality protein within a four to six hour window around training (including pre-workout meals) is sufficient for most people. If you train fasted, it’s important to get that protein in sooner, ideally within a 1-hour time window post-exercise. However, when it comes to timing, your daily intake matters most.
The important thing is protein quality. Animal-derived proteins are generally more digestible and tend to be higher in leucine, a key amino acid for stimulating MPS versus plant protein. That said, you can absolutely get high-quality protein on a plant-based diet with just a bit of planning.
Because I was still consuming animal products during the challenge (eggs and dairy), I was able to easily get complete protein sources. While you can still get complete proteins on a vegan diet, it can be a bit trickier. Certain plant proteins contain a partial chain of amino acids, but you can get a full profile by combining proteins like legumes and grains (rice and beans) or nuts/seeds with complementary foods.
To be considered a complete protein source, the food must contain all nine essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Quinoa, tofu, tempeh, edamame, chia seeds, hemp seeds, and nutritional yeast are often cited as complete or near-complete protein sources.
Many grains are lower in lysine but higher in methionine, and legumes are rich in lysine but lower in methionine. Pairing foods like chickpeas, lentils, black beans, peanuts, and cashews with grains like bread or rice will give you everything you need. Pita and hummus, a PB&J sandwich, rice and beans—you can get creative with combos. Throw some tofu in there or add a protein shake, and you don’t need to worry about protein at all. It’s easier to hit very high protein targets with animal products, but it’s absolutely possible on a vegan diet too.
I didn’t track my protein with an app during the 30 days, but I had a general sense of how much I was eating because I used to track meticulously, and much of my diet stayed similar.
I weigh around 142 lbs, and usually aim for the “1g of protein per lb of body weight” rule as a general guideline (140-150g/day), but I don’t follow it religiously. Some days I consume slightly less, some much more, and I haven’t noticed material changes to my muscle mass or strength performance because of daily fluctuations.
The last point I found interesting is the role of fast vs. slow twitch muscle fibers. Endurance athletes and long-distance runners tend to have more slow-twitch muscle fibers, and sprinters/powerlifters rely more on type II fibers. According to the meta-analysis, there has been no evidence to-date that a specific diet can alter the fiber type in humans. As Maybelline says, “Maybe you’re born with it.”
Overall, I didn’t see notable increases in strength, but didn’t see any decreases either. The research concluded that vegan and vegetarian diets “may elicit potentially disadvantaged properties for strength performance,” but that’s mainly if we don’t plan. If you (1) get adequate protein, (2) cover essential amino acids, and (3) follow a progressive resistance training plan, and 4) get adequate calories, the diet itself likely isn’t the limiting factor for your gainzzz.
My Overall Experience
I found the first 30 days much easier than expected. I didn’t feel deprived or like I was missing out. I never felt like I was counting down the days until I’d be reunited with my beloved meat again. Instead, it felt like a natural transition, one where I could satisfy textural cravings with a wide variety of vegetarian options. I realized perhaps it wasn’t the meat itself I craved, but the texture — the chewiness and toughness I could replicate with a tofu steak.
While I still ate animal products, mostly egg whites and cottage cheese, which also contribute to one of humanity’s worst industries, I felt a bit better knowing I was doing a small part in not eating animals. That alone gave me a lighter energy throughout the day. Arthur Schopenhauer once wrote, “The world is not a factory and animals are not products for our use,” and that was a recurring thought over the past two months.
I enjoyed cooking again and becoming more creative in the kitchen. And I really loved continuing to share food with my partner Kenz (one of my top love languages).
After a smooth, easy, enjoyable first few weeks, my first roadblock came around mid-month, and it was an aesthetic one. My skin was going nuts. Cystic acne began forming all over my back and face. While I was workshopping the cause of my reaction, it struck me: I remembered back in 2020 that I experienced the same outbreak. The culprit? Fake meat brands—worst of all being Gardein and Yves.
With experimental lifestyle changes, instead of scrapping the whole thing because one piece isn’t working, we can use creativity to rework and try again. Sometimes it’s just a matter of experimenting more. In my case, it meant trying different brands.
I immediately cut out the processed fake meat, and voilà: my skin cleared up instantly. After that, I found brands that worked better. Beyond Meat and Impossible seemed okay occasionally, and some days I skipped fake meats altogether and got protein sources elsewhere.
Eating Out
I wasn’t sure if I’d really enjoy eating out as much, but Kenz took me to so many different vegetarian places and I was blown away by how much some of the dishes resembled meat. There’s a vegan sushi spot in Vancouver called COFU Pressed Sushi that made sushi which mimicked meat. On the menu you can find meatless salmon, tuna, eel, and ribeye pressed sushi. Beautiful presentation and even better taste. Many restaurants in Vancouver offer a wide array of vegetarian options with some of our go-to faves being Tacofino, Meet, Keefer Bar, Kokomo and Virtuous Pie. While there are some restaurants that are meat-heavy and offer very little veggie options, most places do accommodate different diets and do it quite well.
A Full Day of Eating Veggie
Because I’m a gal who loves full days of eating content, I’ve included a sample day on the vegetarian diet below with calories and macros included. On average, I eat around 2,200 calories per day and increase that amount significantly when I’m deep in training. Overall, I’m eating slightly less protein and more carbs than I did when eating meat, but I’m okay with that.
Meal 1 (Breaky): Protein pancakes
*flourish pancake mix, blueberries, sugar-free maple syrup, vegan butter
Calories: 408
Protein: 23g
Carbs: 56g
Fat:10g
Meal 2 (Snack): Oreo Protein Bar + Greens Juice
*Base Pro greens powder (cherry), citruline malate 1:1, creatine, celery, cucumber, spinach
Calories: 316
Protein: 24g
Carbs: 32g
Fat:12g
Meal 3 (Lunch): Spinach Feta Egg White Wrap + Cucumber
Calories: 290
Protein: 19g
Carbs: 33g
Fat: 10g
Meal 4 (Snack): Vegan Jerky (1/2 pack)
Calories: 110
Protein: 7g
Carbs: 17
Fat: 2g
Meal 5 (Snack) – Protein Smoothie
*unsweetened almond milk, vanilla cupcake protein powder (vegan), blueberries, spinach, almond butter
Calories: 286
Protein: 26g
Carbs: 17g
Fat: 13g
Meal 6 (Dins): Tofu Tacos
*gluten-free breadcrumbs w/ egg wash, rice wine vinegar-based slaw, home-made guac
Calories: 595
Protein: 27g
Carbs: 67g
Fat: 28g
Meal 7 (Snack): Mid-Day Square
Calories: 170g
Protein: 6g
Carbs: 6g
Fat: 13g
Totals
Calories = 2,175
Protein = 132g (24%)
Carbs = 228g (42%)
Fat = 88g (36%
*totals are approximate
Final Thoughts
I’m not sure whether I’m going to go strictly vegetarian, eat meat on occasion, become lacto-ovo vegetarian, or pesco-lacto-ovo vegetarian long-term. I do know that rigid labels and restrictions can manifest guilt when I veer off course.
So I’m going to continue on my lacto-ovo vegetarian diet for the most part, and if things change down the road, things change.
If you’ve been interested in trying one of these diets or worried about deficiencies and micro- and macronutrients, a bit of planning (and perhaps supplementation) can quell those apprehensions. Research on the impact of vegan and vegetarian diets on strength and endurance performance is still relatively scarce, with conflicting results.
As I always say: try it for yourself. Keep tabs on your mood, energy levels, and satiety, and how well your diet and lifestyle align with your values.
If you’ve experimented with eating vegan or vegetarian, I’d love to hear what changed for you. Feel free to share in the comments below 🙂