We all want to eat the kinds of foods
that make us feel better and live longer.
But there’s so much conflicting information out there,
so many nutrition opinions.
Welcome to the Nutrition Facts Podcast,
I’m your host, Dr. Michael Greger.
It’s my job to give you the information you need
to make the healthiest choices possible.
Today we discover how plant-based diets improve the performance
of athletes and nonathletes alike.
In my video about comparing vegetarian and vegan athletic performance,
endurance, and strength, I discussed a 2020 study that found
that vegan athletes—even though they were significantly older—
had significantly superior aerobic capacity and endurance,
lasting 25 percent longer on a time-to-exhaustion cycling test.
The question is why?
One potential mechanism that could explain the greater level
of endurance performance in vegans may be a higher amount
of carbohydrate intake, which could lead to better endurance
performance through higher muscle glycogen storage.
Other potential mechanisms that may explain the better endurance
performance in vegans could be due to the anti-oxidant
and anti-inflammatory profiles of their diet.
Maybe it’s even their hearts.
Yet another study showing superior VO2 max in vegan athletes,
meaning superior aerobic capacity:
this time they also did echocardiograms,
looking at their hearts in real-time using ultrasound,
and the lower relative wall thickness
and better main ventricle systolic and diastolic function
in the vegans are most likely positive ﬁndings.
Now wait a second. Given the higher VO2 max reached
by the vegan athletes, maybe they were just better trained
than the nonvegan athletes, and that’s why their hearts
looked like they were working better.
However, the weekly training frequency and running distance
were similar in both groups, suggesting benefits
even with the same amount of training.
So, it’s important to educate healthcare professionals;
so they don’t try to discourage a vegan diet
and may even want to consider telling folks implementing
an exercise training program to give it a try.
But you don’t know if it has the same kinds of effects
in nonathletes, until you...put it to the test.
A vegetarian vs. conventional calorie-restricted diet:
the effect on physical fitness in response to aerobic exercise
in patients with type 2 diabetes.
Diabetics were randomized to the same caloric restriction,
the same exercise, but just vegetarian versus nonvegetarian.
They provided all the meals so they could ensure compliance
and closely monitored the exercising.
VO2 max increased by 12 percent in the vegetarian group,
significantly better than in the non-vegetarian group
who didn’t significantly improve at all.
Maximal performance increased by 21 percent in the vegetarian group,
again, significantly better than in the non-vegetarian group
who didn’t significantly improve at all.
In other words, the results indicated that more plant-based diets
led more effectively to improvement in physical ﬁtness
than less plant-based diets,
after the same aerobic exercise program.
It seems that those eating vegetarian
were able to better burn off
carbohydrates compared to nonvegetarians,
and had better insulin sensitivity,
both markers of improved metabolic ﬂexibility,
meaning the ability to switch back and forth
between burning sugar and fat.
Besides physiological mechanisms,
there may also be psychological factors.
They observed reduced hunger and reduced feelings of depression
in the vegetarian group which may have given them
a more positive attitude towards exercise.
Here’s the psychological data.
Those randomized to eat vegetarian had a greater improvement
in quality of life and mood.
They felt less constrained, meaning the calorie restriction
didn’t seem as burdensome;
they had less disinhibition,
meaning less tendency to binge and overeat,
along with maybe less feelings of hunger.
Not to mention the superior effects of a vegetarian diet
on body weight, glycemic control, blood lipids,
insulin sensitivity, and oxidative stress.
Wait, better body weight?
I thought they were given the same number of calories.
Yes, both diets were isocaloric, the same calories,
yet just eating meat-free led to significantly more weight loss—
about six pounds more; more waist loss, a slimmer waist;
lower cholesterol, of course; and less superficial fat,
meaning the external jiggly fat;
and most importantly, significantly more visceral fat loss,
the most metabolically dangerous deep belly fat.
Same calories, yet more loss of body fat.
And not surprisingly, better control of their diabetes.
All in addition to leading more effectively
to improvements in physical ﬁtness.
Did you know that long- term plant-based eating
may improve exercise capacity and endurance?
Here’s the story.
Few studies have investigated the impact of a plant-based diet
on athletic performance, but the majority of the studies
that have been done show no differences in endurance, performance, or strength.
So, while plant-based diets do not seem to provide advantages
or disadvantages on exercise performance,
what plant-based diets can do is reduce the risk of chronic disease.
This is a point I made in my video
Why All Athletes Should Eat Plant-Based Diets,
because surprisingly, endurance athletes may have
more advanced atherosclerosis and more heart muscle damage,
compared with sedentary individuals.
So, it’s even more important they eat healthy.
But due to the favorable impact on health,
it could be assumed that performance would also be influenced
by plant-based diets.
Let’s take a closer look at the available evidence.
This is the most commonly cited review.
Studies connecting vegetarian diets to improved health
are well-established;
however, the evidence for this phenomenon to be transferred
to improved physical performance in athletes is less clear,
finding no differences —at least acutely—
between a vegetarian-based diet and an omnivorous diet
in muscular power, muscular strength, short burst, or endurance performance.
The intervention studies in this review, however, only lasted days or weeks.
So, being a vegetarian for four days may not tip the balance,
or even a few months, but that’s a considerable limitation.
These are people who have been eating meat
their whole lives
and subsequently adopt a vegetarian diet only
for the duration of the study, rather than comparing participants
who have adhered to a vegetarian or meat-containing diet long-term.
This study compared exercise capacity of vegan, vegetarian,
and meat-eating recreational runners and found
similar maximum power output among all three groups,
suggesting there’s no significant difference in maximum exercise capacity.
But that’s at the same training frequency, time, and distance.
Perhaps plant-based diets might enhance recovery
and allow such athletes to train longer and harder?
A number of studies have come out since this review
was published in 2016. What’s the update?
Well, this study compared the cardiorespiratory fitness
and peak torque strength differences between vegetarian
and omnivore endurance athletes.
Most of the vegetarians were actually vegans
and most or at least two years and…
results from this study indicate that
vegetarian endurance athletes’ cardiorespiratory ﬁtness
was greater than that for their omnivorous counterparts.
They had a greater VO2 max,
meaning a greater maximal oxygen uptake,
greater aerobic capacity as measured on a progressive,
graded, maximal treadmill test to exhaustion,
though peak torque, peak strength based on leg extensions
didn’t differ between diet groups.
Bottom line: these data suggest that vegetarian diets
do not compromise performance outcomes
and may facilitate aerobic capacity in athletes.
In this 2020 study, all the plant- based participants were eating vegan
for an average of four years.
So, they were essentially comparing those who ate meat for 21 years
versus those who ate meat for 25 years.
But after four years eating plants,
you might expect to see some sort of difference.
Yet, no signiﬁcant differences were noted for upper
and lower body muscle strength, like in the last new study.
Both groups of athletes were comparable for total body weight
and lean body mass, though age was signiﬁcantly higher in vegans
compared with omnivores;
so, that put them at a little disadvantage.
Yet still, there it is again.
Significantly better aerobic capacity.
Then, they had them pedal until exhaustion,
and the vegan group lasted about 25 percent longer—
12 minutes as opposed to 9 minutes.
Is that just because their aerobic capacity is so high?
No, even after controlling for VO2 max levels, there was still
a signiﬁcant endurance advantage in the vegans.
The researchers conclude that in the very least,
a strictly plant-based diet doesn’t seem to be detrimental
to endurance and muscle strength,
and endurance might actually be better in vegans,
contrary to popular belief.
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To see any graphs, charts, graphics, images, or studies mentioned here,
go to the NutritionFacts Podcast landing page.
There you’ll find all the detailed information you need –
plus, links to all of the sources we cite for each of these topics.
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