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The World’s Best Diet Doesn’t Make You Lose Weight
The World’s Best Diet Doesn’t Make You Lose Weight
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0:00
If you’ve been alive anytime in the last… centuries,
0:03
you haven’t been able to avoid the concept of diet programs.
0:06
Since 1864, when an early fad diet sang the praises of the low-carb lifestyle,
0:12
we’ve been inundated with diet books, ads, and storefronts.
0:16
A lot of these diets come and go, but some of them have real sticking power,
0:19
especially when they’re reflective of established nutritional patterns.
0:23
One diet you’ve probably heard of is the Mediterranean diet.
0:26
And one of the reasons you may have heard of it is that it actually works.
0:31
Like, weirdly well.
0:33
And in some ways, it doesn’t seem like it should work. So what does the research say
0:37
about this pattern of food intake, and how do we even go about researching this at all?
0:41
Diet advice should be taken with a grain of salt,
0:44
but maybe this one could be taken with a dash of olive oil.
0:48
[♪ INTRO]
0:51
Real quick, this video is about diet stuff, including things like calorie restriction.
0:55
If that’s not a cool topic for you, we don’t mind if you want to skip this one.
0:58
Officially speaking, the Mediterranean diet describes the typical pattern of
1:02
eating in Crete and southern Greece around 1960.
1:05
Similar diets come from other areas of the Mediterranean Basin,
1:08
including southern Europe, northern Africa, and western Asia.
1:12
In other words, areas that grow a lot of olives.
1:15
Those olives are critical, not because of martinis,
1:18
but because one of the notable features of the Mediterranean diet is that olive oil
1:22
is the primary source of fat, and it is not used sparingly.
1:26
In fact, up to 40% of the calories for people who eat this way come from fat.
1:31
For a long time, the prevailing wisdom was that that much fat was not a good thing,
1:35
but as we’ll see, this diet proves otherwise.
1:38
The diet also includes a lot of fruit, vegetables, nuts, breads, and other plants, low or moderate
1:44
amounts of fish, poultry, dairy, and red wine, and low amounts of red meat and processed sugars.
1:49
So to be clear, the Mediterranean diet is not a fad diet, it’s just...
1:54
the diet of Mediterraneans.
1:56
While yes, there are tons of contemporary cookbooks with attractive influencer-types
2:00
on the cover, the dietary pattern has actually been officially recognized
2:04
by UNESCO as a cultural heritage connected to its geographical origin.
2:09
The first epidemiological study of the diet began in 1958, collecting
2:14
decades of research on middle-aged male residents of seven countries.
2:17
In the years since, it’s become one of the most well-studied dietary patterns in the world.
2:22
But it’s tough to study the impacts of a diet.
2:25
In an ideal world, we’d do a randomized controlled trial,
2:28
where large numbers of participants are sorted into groups, one group follows the
2:32
Mediterranean diet for decades, and one group eats other stuff.
2:36
But that’s not really possible with something as comprehensive as a dietary pattern.
2:41
Getting tens of thousands of people to change
2:43
their entire diets for decades for a scientific study is a huge ask.
2:48
But randomized controlled trials are the gold standard in health research,
2:52
and it’s not like you can’t do them at all.
2:55
Where it makes sense is on shorter timeframes to study what are called surrogate markers.
2:59
These are intermediate health outcomes that relate to a specific diagnosis or endpoint,
3:04
which you can use to approximate how that endpoint is going.
3:08
So, for example, you can use blood pressure or cholesterol as a surrogate
3:12
marker for coronary heart disease, or serum estradiol for postmenopausal breast cancer.
3:17
And it’s a lot easier to keep track of what somebody eats for a year and see
3:22
how that affects their LDL cholesterol than to ask them to change their diet for decades
3:26
to see whether they eventually develop coronary heart disease.
3:30
Researchers complement these shorter randomized controlled trials with prospective cohort studies.
3:35
In this type of study, researchers follow
3:37
groups of people before any of the outcomes they’re studying occur.
3:40
So if you wanted to study whether the Mediterranean diet affects the
3:44
development of heart disease, you wouldn’t select participants who already had heart
3:48
disease to see how following the Mediterranean diet affected it.
3:51
You’d select participants, track what they eat over long periods of time,
3:55
and follow who gets heart disease at what point.
3:58
Mediterranean diet studies typically aren’t separated into simple,
4:01
“yes this person follows the diet, no this person doesn’t”.
4:04
Instead, they use a score that assigns points to different aspects of the diet,
4:08
like a D&D character sheet.
4:10
Participants get a rating on 9 different components.
4:12
For example: do they eat more fruit and nuts than most people?
4:15
Do they eat more vegetables, do they eat less meat, do they drink moderate amounts of alcohol?
4:20
In these types of prospective studies, that allows researchers to see when
4:23
participants follow Mediterranean eating patterns more or less closely.
4:27
If people are more likely to develop heart disease when they’re eating less like the diet,
4:31
that can suggest that the diet is related.
4:34
By combining results from these two types of
4:36
studies, researchers can make a stronger claim about causality.
4:39
Basically, you have indirect evidence from the observational study that
4:43
following the diet more closely over the long term reduces heart disease.
4:46
And you have direct evidence from the
4:48
interventional studies that the diet lowers LDL cholesterol.
4:51
Put these together, and scientists can make a
4:53
pretty compelling case that the Mediterranean diet lowers the risk of heart disease.
4:57
And while the actual research methods are a little complicated, they tell us a lot.
5:01
A 2021 comprehensive review looked at studies of the impact of the Mediterranean diet on
5:06
seven different health outcomes and rated the strength of the research on a zero to four scale.
5:11
Zero represented no evidence of a link, and 4 represented convincing evidence of
5:15
a link backed up by multiple lines of evidence of the types we’ve discussed.
5:20
And none of the health outcomes they looked at scored below a two, which means there was at
5:25
least suggestive evidence of the Mediterranean diet having an impact on every single one.
5:30
We’ll get into the specifics in a moment,
5:32
but first, all science needs funding, so here’s a quick break.
5:37
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And right now, SciShow viewers can save 20% off an annual subscription at brilliant.org/scishow.
6:22
The strongest evidence category starts off with cardiovascular disease, where cohort studies
6:27
show that higher Mediterranean diet scores are associated with lower risk of coronary
6:31
heart disease, reduced risk of stroke, and fewer cases of and deaths from cardiovascular disease.
6:37
The Mediterranean diet also lowered blood pressure, blood lipids like cholesterol,
6:41
and markers of inflammation in intervention studies,
6:44
giving it a big thumbs up for its ability to improve our heart health.
6:47
Diabetes is also in this category, with cohort studies showing that people who
6:51
follow a Mediterranean diet have a lower risk of type 2 diabetes, and intervention studies
6:56
showing that type 2 diabetes patients that follow the diet have better glycemic control.
7:01
Rounding out the convincing evidence is metabolic syndrome, which makes sense because metabolic
7:06
syndrome relates to risk factors for both cardiovascular disease and type 2 diabetes.
7:10
In prospective studies,
7:11
people who eat the Mediterranean way have lower risk of metabolic syndrome,
7:15
and in intervention studies it’s more likely to go into remission when people follow the diet.
7:19
That’s a really strong start for the Mediterranean diet.
7:22
In that same review of health impacts, the “highly suggestive” category reflects health
7:26
outcomes with 3 or more observational studies reporting a relationship with
7:30
the Mediterranean diet, with no studies that clearly refute them.
7:34
Cognitive function fell into this category, with adherence to the Mediterranean diet being
7:39
associated with lower risk of Alzheimer’s disease and age-related cognitive decline.
7:43
Cancer was also in this category.
7:45
There’s evidence of a relationship between the Mediterranean diet and lower risk of breast
7:49
cancer, as well as lower overall rates of cancer incidence and cancer deaths.
7:54
Our final category are the health outcomes
7:56
where the evidence is suggestive that the Mediterranean diet can make a difference.
8:00
By suggestive, the researchers mean there are one or two studies that support the link,
8:04
and no studies that clearly refute it.
8:07
To start off, while overall cancer risk and death were in the highly suggestive category,
8:12
most specific cancers fall here: specifically,
8:15
colorectal, head and neck, respiratory, gastric, liver, and bladder cancer.
8:19
Overweight and obesity fall in this category, too.
8:22
It may seem counterintuitive because culturally speaking,
8:26
we tend to associate the concept of “diets” with weight loss.
8:29
We also tend to associate the idea of weight loss diets with low-fat,
8:32
and this is far from a low-fat diet.
8:35
That’s why some doctors don’t recommend it as
8:37
often for weight loss as they do for other health concerns.
8:40
There is, however, compelling evidence that the Mediterranean
8:42
diet doesn’t cause weight gain or increases in waist circumference.
8:46
And when it comes to losing weight and fat, there is some evidence that the Mediterranean diet is
8:50
more effective than some other diets when people are restricting how many calories they’re eating.
8:55
So it’s possible that eating 1600 calories a day of a Mediterranean diet may result in greater
9:00
weight and fat loss than eating 1600 calories a day in just a general calorie reduction.
9:05
A calorie-unrestricted Mediterranean diet doesn’t seem to do much for obesity,
9:09
so researchers are thinking that reducing calories is still
9:12
more important than the specific nutrients you get on the Med diet.
9:15
And finally, there’s total mortality.
9:18
Cohort studies do indicate that eating a Mediterranean diet is
9:21
associated with a reduction in total overall mortality.
9:24
The evidence here is merely “suggestive” though, because it’s really hard to do
9:28
long-term intervention studies where the outcome you're measuring is, you know.
9:33
Death.
9:34
But, it makes sense, given that the Mediterranean diet is associated with
9:37
a lower risk of death from all of the specific causes we just listed out.
9:41
But it’s not just that.
9:43
The diet is also associated with longer telomeres.
9:47
Telomeres are sections at the end of chromosomes that are known
9:50
to be shorter in connection with cell damage through stress and inflammation.
9:54
They are typically what people talk about when they say “cellular aging”.
9:57
Longer telomeres indicate slower age-related biological processes,
10:01
which could result in lower mortality.
10:04
But researchers are still trying to figure out exactly why the
10:07
Mediterranean diet has such broad health effects.
10:09
One approach is to look at the different parts of the diet as individual pieces.
10:14
For example, the high intake of fruit and veggies may be what impacts cognitive
10:18
functioning, and the inclusion of nuts may be the reason for better heart health.
10:22
If that’s the case, then the reason that the Mediterranean diet has so many health
10:25
effects would be that there are so many different healthy parts of it.
10:28
But there does seem to be more to it just than that.
10:31
Researchers are now studying the way that the different parts of the diet
10:34
and different nutrients interact with each other.
10:36
One hypothesis is related to inflammation and oxidative stress, which can cause cell damage.
10:41
That cell damage can lead to cardiovascular disease, cancer,
10:44
dementias, and diabetes, just to name a few.
10:47
And there’s evidence that the Mediterranean diet
10:49
improves several different indicators of inflammation and oxidative stress.
10:54
Now, we still don’t know the specific pathway by which the Med diet might calm down inflammation.
10:58
It may be that the nutrients involved tamp down on things that cause inflammation,
11:03
ramp up things that prevent inflammation, make cells more resistant to inflammation,
11:07
or change the way the immune system communicates.
11:10
Whatever the mechanism, though, it seems that the Mediterranean
11:12
diet has some really important system-wide effects on our health.
11:16
Even better, the Mediterranean diet isn’t just good for people.
11:19
It’s good for the environment, too.
11:21
Because it’s mainly plant-based, it uses less water and has lower
11:24
greenhouse gas emissions than many other dietary patterns.
11:27
And at least in traditional settings, the meat that’s consumed comes from animals that
11:31
graze among tree crops that already exist, as opposed to growing grains
11:35
specifically for animal feed, which also lowers the environmental impact.
11:39
But we are not doctors, and we can’t recommend you switch to the Mediterranean diet for your health.
11:44
What we can say, though, is that multiple members of the SciShow team have had our
11:48
doctors recommend this diet to us, so take that for what it’s worth.
11:53
But I for one have never turned down an excuse to eat more hummus.
11:56
And if that happens to make me healthier, that sounds like a win-win.
12:00
[♪ OUTRO]
