mediterranean diet or vegan, which one's better? i get that question all the time. lucky for us,
scientists set out to answer it. a new clinical trial compared a mediterranean diet to a low-fat
vegan diet face to face. drama! both are very rich in fruits and vegetables. as the study explains,
mediterranean and vegan diets are variations on a theme. one favors plant-based foods, the other
consists of plant products exclusively. of course plant products aren't necessarily healthy. plenty
of junk foods come from plants. but their low-fat vegan was mostly whole foods. fruits and vegetables,
legumes and grains. the mediterranean diet had all of those plus nuts and seeds and some animal
products. mostly fish, white meat, eggs and low-fat dairy. it also had olive oil and dark chocolate
the chocolate may sound a bit weird, they were basically replicating the protocol of a famous
mediterranean diet study called predimed. okay, so what happened? people on the vegan diet lost weight,
improved their insulin resistance and lowered their cholesterol. people on the mediterranean diet
saw none of those improvements although it was a bit better for blood pressure. so that means vegan
is better than mediterranean right? see, this is the problem with this type of study comparing two
diets head to head. they're always advertised as "diet A beats diet B". i totally get why they do that,
that headline gets more clicks. but it's also the one that teaches us the least. so let's take a look
under the hood. it turns out we can actually learn quite a bit about nutrition and health from this
study if we look past the sound bites. first, the low-fat vegan diet was better for weight loss
people on it lost some weight whereas they didn't lose any significant weight on the mediterranean
diet. why would that be? well, the people on low fat ended up eating less calories. 500 calories less
per day. this study was ad libitum, so people were told what foods to favor on each diet but not how
much to eat so they basically ate as much as they wanted. uh, jealous! where do you sign up for that
study? so it seems like people on low-fat vegan felt full with fewer calories. calorie density
probably comes into play. the low-fat diet was very calorie dilute. fruits and vegetables have a lot
of water and fiber and few calories per gram so we can eat a large amount and fill up with relatively
few calories, whereas their mediterranean diet had a few foods that were more calorie dense
like olive oil and chocolate. but that doesn't mean we can't lose weight on a mediterranean diet! we
have to be very careful with these logical leaps. sometimes people lose weight on a specific diet
and then they assume that's the only thing that works and every human being needs to be doing
the exact same thing they did. one camp says fat is the problem and everybody should be eating low fat
the other camp says, no! it's carbs that make us fat and the only way to lose weight is to cut
carbs. it's not hard to see that these nutrient-centric views don't pan out
this very study we're looking at shows it. the diet with the most carbs, low-fat vegan, was also
the best for weight loss. so clearly carbs don't explain it. so is fat the key to weight loss?
the authors of the study seem to think so, here's a quote from the lead author
"the mediterranean diet caused no weight loss at all, the problem seems to be the fatty fish,
dairy and oil". i don't agree with that take, i mean sure if you take out all the fat yeah
you're going to cut calories but you could just as well leave the fat and take out all the carbs and
you'd lose weight that way too. in fact you don't even need to remove a specific nutrient, you could
just tweak things. people on the mediterranean diet were told to eat 50 grams of olive oil every day
now, that's a few tablespoons, it doesn't seem like a ton, but because of the caloric density of oil
it adds up to almost 500 calories a day, which if you remember was the caloric difference between
the two diets. so we could for example moderate the olive oil and replace some of the chocolate
with some fruit or something like that and through a couple of those tweaks we could probably match
the calories of the vegan diet or even go lower potentially while still on a mediterranean diet
with some olive oil (not as much) and some animal products. so the low-fat diet is okay, the problem
are the extrapolations and starting to fantasize that it's the only way to succeed. it's not. in fact,
trials have compared low-fat and low-carb diets side-by-side, for example this trial from stanford
weight loss was identical on low carb and low fat after a year. that trial had a great name, dietfits
and that's also what they found, either diet fits. however people can control their calorie intake
they seem to lose weight, it doesn't seem to matter too much what specific nutrient those calories
come from. as far as i'm concerned that's fantastic news, it means we're not limited to one path
we can lose weight on low carb, low fat vegan, low fat not vegan, mediterranean, intermittent fasting
they can all work if they're designed with weight loss in mind. so it's less about what i call my
diet, these labels, and more about the how. the specifics of how we do it day to day. and to be
fair the recent study kind of acknowledges that: "a mediterranean diet as delivered in these trials is
not effective for weight loss". so it doesn't mean mediterranean diets can't work, period,
just that the specific design they used didn't. that may sound like i'm splitting hairs but actually
this explains a lot of confusion around nutrition. a scientific experiment is like a google search, it
answers the specific question we ask. in fact, google's better because it has that wise guy
function: "did you mean...?". experiments don't do that, they don't try to guess what you really
meant and help you out, they only answer the exact question you ask, the way you ask it,
at the time that you ask it, the answer, the result, is always perfect, the problem is the
interpretation, the extrapolation. and in fact most confusing messages on nutrition online
don't hinge on scientific results per se, they hinge on the interpretations, on the extrapolations
our mind is constantly pushing us to extrapolate from our observations to find general rules that
explain how the world works. so when we look at a study like this pitting two diets face to face
our natural tendency is to extrapolate. "oh so low-fat vegan is superior i guess"
and media headlines do exactly the same thing because that's what gets the clicks. a big part of
scientific training is having it beaten into us to catch ourselves making those logical leaps. general
rules in science require looking at the whole field and the different pieces of evidence need to
consistently point in the same general direction. i know, kind of a drag. so the accurate headline for
this study would be more like "people who ate only whole plants excluding nuts and seeds ate less
calories than people on an omnivorous diet with 50 grams of olive oil a day and as much low-fat dairy
and dark chocolate as they wanted". not exactly viral material. instead they went with "vegan
beats mediterranean". understandable from the media standpoint, i guess. the problem with that takeaway
is that it's not a general rule. a mediterranean diet could potentially come out on top depending
on the specific design. okay, but maybe because i'm half portuguese i'm biased towards mediterranean
diets and i'm just making all this up. maybe i'm in the pocket of big olive oil
is there any actual evidence that a mediterranean diet can help with weight loss? here's a different
trial where a mediterranean diet outperformed low fat for weight loss. so kind of the opposite
of the recent study, it would seem. oh my god, scientists can't agree on anything, i'm just
going to start flipping coins to decide what to eat! no, what this all tells us is that there are
several moving pieces, it's more nuanced than just "this diet wins". it's not the world cup. that's why
excessive focus on individual studies and flashy headlines can be confusing. a well-controlled study
that lasts for a couple months is great but the real goal is a dietary pattern that's both
healthy and sustainable long-term for you. the best diet is the one you can actually eat. some people
do better with no temptation. strict diet, not a drop of oil, zero sugar, in the zone. and they can
stick with that for years and actually enjoy it and if they start straying and indulging a little
bit everything goes off the rails. other people find it impossible to stay on a monastery-style
strict diet long term, they prefer to have a little bit of oil or a little bit of sugar
once in a while while still staying reasonable on total calories. personally i find it easier to lose
weight by going easy on the oil but that's just an anecdote, who cares? some people lose weight on high
fat diets, others on low carb diets. it's just like exercise, if i started saying that lacrosse is the
only good form of physical activity and everything else sucks nobody would take that seriously, but
that's what we do with food. we get into these religious camps of super low fat or low carb and
everything different is heresy and anyone who's not doing my exact diet is a moron. obviously
there are some fundamentals for health, flexibility doesn't mean that everything is equally healthy
no healthy dietary pattern is packed with junk food or huge amounts of salt or saturated fat
but within that healthy range there's plenty of wiggle room, several valid choices. okay,
how do we know this is actually true? maybe low-fat vegan is better for every human being
and i'm just trying to sound politically correct because i need everybody to like me
is there any actual evidence for this individual response to diet or did i just make that up?
actually, the recent study itself shows it. they randomized the volunteers to one of the two diets
but after a while, they swapped the groups and tested each person on the other diet as well. this
is called a crossover design and it allows us to see not just the average of the entire population
but how each person did on each diet. here's the weight change for each participant in the study
on each diet. brown bars is mediterranean, green is low-fat vegan. each pair of bars is one person. so
here's someone who lost a lot of weight on low-fat and gained on mediterranean
here's someone who lost on both, more on low-fat. this person lost more on mediterranean
than on low-fat. this one lost on mediterranean and gained on low fat, and this one gained on both
now maybe they gain weight because that diet is not a good fit for their physiology
or maybe they're cheating a little bit because they couldn't stick with it. either way it's not
a good fit long term for that person. bottom line, even within this one study, with the specific diet
composition they chose, we see this individual variation from one person to another. most people
lost more weight on low fat, sure, but some didn't. viewers sometimes comment on our videos that the
studies we're showing must be wrong because their individual experience is different
so it's important to understand these things are not contradictory. variation is inherent
to biology. we can look at trends in a population while still being aware of individual variability
science gives us a general direction but how you get there, the specific path you take,
can and should be adapted to our individual characteristics and preferences. okay, last thing
about weight loss: we have this societal obsession, gotta lose weight at any cost. but what we really
mean is fat loss. we don't want to lose lean weight. in the study, people on low-fat vegan lost weight
and most of that was fat but 40% was lean weight. so probably some loss of muscle along with the fat
now, that didn't make the headlines. but it seems like an important point. so does that mean going
vegan causes you to lose muscle? maybe all those stereotypes were right! no, it's the same logic,
we have to be careful with the knee-jerk extrapolations. people on low-fat vegan went
from 80 grams of protein a day before the study to less than 40 on the diet. that's less than the RDA
even for women. during weight loss your body is starving for calories so it sheds fat but it also
sheds some muscle. the way to minimize that is resistance training and solid protein intake. so
muscle loss is not a low fat problem, it's not a vegan problem, it's a low protein problem. you
could lose weight on a low fat vegan diet if you wanted and potentially keep your muscle
by optimizing those factors we just talked about. like trying to eat a good amount of protein- rich
foods. if you're completely plant-based it would be legumes, nuts, maybe protein powder for some people
we made a whole video on plant protein. alright, enough about the weight. the low-fat diet also
improved insulin resistance. insulin resistance means your body produces insulin but it doesn't
function normally and if insulin resistance continues it can lead to full-blown diabetes
so right off the bat this finding contradicts another common internet myth. there's this idea
out there that eating carbs causes diabetes and the only way to improve your glucose metabolism
is to cut all carbs regardless of quality. but here we see the diet with the most carbs, low-fat vegan,
was the one that improved insulin resistance. the carb intake on the mediterranean diet was lower
and yet insulin resistance did not improve so it's the exact opposite of the "carbs cause
diabetes" idea. so again, we have to be very careful with these knee-jerk conclusions. now, can people
improve their insulin resistance and diabetes on a low-carb diet? absolutely, it's been done.
on low-carb diets, on high-carb diets, so it's not primarily about carbs. carbs don't cause diabetes
okay, so what does explain it? insulin resistance is heavily affected by calorie balance and weight
loss, we consistently see improvements in insulin resistance and diabetes in trials where people
lose weight, independent of the diet used. in the words of some diabetes experts: "substantial weight
loss achieved by any means can bring about remission of type 2 diabetes". that's not to
say that every form of weight loss is healthy but there are many ways to lose extra fat and
they tend to also improve insulin resistance and diabetes. so it's not surprising that in our study
the low-fat diet improved insulin resistance since we saw that it helped with weight loss.
in fact, if you remember that older trial where the mediterranean diet was better for weight loss,
lo and behold it was also better for insulin resistance and glucose control in that trial. so
again, it's less about the label, the name of the diet, and more about how it's actually done. the
calorie balance, can people stick with the diet, do they lose weight etc. okay, let's take a look
at cholesterol. in the trial, low-fat vegan also improved cholesterol levels. it's interesting that
the same diet improved cholesterol and glucose metabolism. sometimes we get comments saying
"why are you talking about cholesterol? i'd rather have high cholesterol than be a diabetic". as if
we had to choose between the two. there's some internet myth that diets that improve cholesterol
mess up your glucose. any healthy dietary pattern should improve both parameters at the same time
if your diet is forcing you to choose between cholesterol and glucose that's probably not plan A
okay, so the low-fat vegan diet lowered cholesterol levels. serum cholesterol is mainly about how much
saturated fat we eat. in the trial, people on the low-fat vegan diet ate 3x less saturated
fat. they also ate 10x less cholesterol and a bit more fiber. so the improvement in serum
cholesterol is completely expected. now, could we tweak the mediterranean diet to match that
performance? i don't know if we could match it but we could certainly improve it by lowering
the saturated fat content in the mediterranean diet. now, some people might say "well, you're just
veganizing the mediterranean diet, thank you very much". but that's kind of the point, these labels are
a construct, in reality these parameters are all sliding scales. the calories, the saturated fat, the
protein. once you understand what the key factors are you can fine-tune them to find what works best
for you. obviously we're talking about the health angle, the physiological consequences. if you're
vegan for ethical reasons or for the environment that's a different story. but even within the vegan
diet there's enormous wiggle room with all these parameters. so, if you want to do a low-fat vegan
pattern, go for it. just make sure you're getting your essential fats and your fat-soluble vitamins
and favor whole unprocessed foods. but if for some reason that diet is not a fit for you, you're not
condemned to being unhealthy and overweight, you can do a diet that is higher fat or lower carb
and still very healthy by keeping the key principles in mind. quick note on blood pressure:
both diets improved blood pressure in this trial, the mediterranean diet a little more
blood pressure control is largely about lowering sodium and increasing potassium
so a lot of fruits and vegetables, unprocessed plants, and easy on the added salt. this study
didn't measure sodium intake so we don't have all the details but on a low-fat vegan or a
mediterranean diet it is very doable to optimize your sodium and your potassium and improve your blood
pressure. here's more on weight loss and a deeper look at cholesterol control. see you next time