- Carbs have a unique metabolic effect that makes us fat.
At least, that's the idea sold by Mr. Gary Taubes,
Dr. David Ludwig, and other low carb enthusiasts.
But it's time they admit that they're wrong.
Taubes and co. believe that carbohydrates drive obesity
because it raises the hormone insulin.
Insulin is said to block the release of fat
and also drive additional fat storage.
This is known as the
carbohydrate-insulin hypothesis of obesity,
but studies continually show that it's wrong.
The latest trial to compare these two eating patterns
was a tightly controlled metabolic ward study,
which means no cheating on the diet.
It was run by Dr. Kevin Hall
and ironically funded by Taubes's own NuSI organization.
For four consecutive weeks, 16 overweight or obese men
were fed a standard American diet, quite high in carbs,
about 50% carbohydrate, 15% protein, and 35% fat.
According to the sample menu published,
it included loads of refined carbs,
including lemonade, granola bars,
pretzel sticks, and sandwich bread.
Participants were then immediately switched
to a very low carbohydrate ketogenic diet,
which was 5% carbohydrate, 15% protein, and 80% fat
for another four weeks.
So both the high carb diet and the low carb ketogenic diet
were equal in calories and protein
and subjects had no access to any outside foods
for the entire eight week period.
OK, so what do you think happened?
Well after the first four weeks on the high carb diet,
participants actually lost 1.1 pounds or half a kilo
of body fat on average.
Switching to the low carb ketogenic diet
for the next four weeks led to a significant dip
in insulin levels by almost half.
However, once again participants only lost
another 1.1 pounds or half a kilo of body fat.
So the high carb diet was just as effective
for fat loss as the low carb diet
despite far higher insulin levels.
This just adds to the mounting evidence
disproving the carbohydrate-insulin hypothesis.
To be fair, although there was no difference in fat loss,
the low carb ketogenic diet did increase
metabolic rate by about 40 calories on average
by the end of the four weeks.
Now this was actually the main aim of the study.
Even if that 40 calorie advantage
remained for an entire year,
which is equivalent to about
14,600 extra calories expended per year,
it likely equals only four pounds or two kilos
of weight loss after two to three years
if you don't cheat on your ketogenic diet.
That may be statistically significant,
but it's certainly not clinically significant.
Many low carb enthusiasts will pick up the design of a study
to challenge its validity,
but this was not the first well-controlled clinical trial
to show that carbs and insulin do not make you fat.
In fact, it was shown over a decade ago
in a six week trial of 20 subjects.
Participants were randomly assigned to follow
either a ketogenic diet 5% carbs
or a moderate carb diet 40% carbs
and there was no difference
in average weight loss or fat loss
and all food and beverages
were provided to participants as well.
You can see in the graphs that, if anything,
strictly cutting carbs leads to
less fat loss as time goes on.
There has also been a smaller and slightly different
version of the NuSI study that I talked about first,
which was also run by Dr. Kevin Hall.
His team found a reduced carb diet,
which was 29% carbs, resulted in less fat loss
than a reduced fat diet, which was 7.7% fat.
At the time, their computer model even predicted
the trend seen in that latest study.
Now for that study, low carb enthusiasts were arguing
that the reduced carb diet was not low carb enough,
but it still lowered insulin levels considerably
and despite this change there was no fat loss advantage
compared to the low fat diet.
Now just to clarify the message of this video,
that's not to say carb-laden junk foods
and soft drinks are off the hook.
They are undoubtedly the biggest contributors
to excess calories and therefore one of the main drivers
of obesity and related health problems.
Remember that clinical trials where the diet
is strictly controlled for is the gold standard
of scientific evidence in this area.
These deserve the most weight
when we consider all the evidence
and they all show that carbs are not uniquely fattening,
whether that's adding more carbs into the diet
or cutting carbs for weight loss.
There's loads of other studies
I haven't even mentioned here, too,
including other trials, observational studies,
and historical evidence, which together all disprove
the carbohydrate-insulin hypothesis.
I'll end it with this.
If you enjoy a very low carb eating pattern
and it's improved your health,
then there's no reason to stop.
It may even be superior to low fat
for managing Type II diabetes
and other metabolic health conditions.
Just know that cutting carbs is definitely
not the only way to get healthy and lose weight
so stop telling people that it is.
Thanks for watching.
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