THE QUICK READ
• High protein, low-carb diets such as
Atkins, paleo and ketogenic will almost
certainly stimulate weight loss – but
they are unsustainable for most people
in the longer term
• If you persist on a low-carb (or any
extreme) diet, against all the urges to do
otherwise, your body will eventually
adapt to it
• The more you restrict your nutrient
choices, however, the more you risk
losing metabolic flexibility and will
find it difficult to shift to a different
dietary pattern
• A high-protein, low-carb, high-fat diet
poses a potential risk in terms of longevity
• The longest-lived, healthiest populations
on the planet are those who consume a
lower-protein, high-carb whole-food diet.
training. Matthew will be following a trend
seen among many fit young people as they
enter their twenties and thirties, planting
the seeds for chronic health problems in his
forties and fifties.
What should Matthew do? To avoid
weight gain, he needs to limit his calorie
intake to 2,550 kcal, while also satisfying his
ravenous protein appetite, with its higherthan-necessary
demand for 135 grams of
protein each day. To do that, he’ll simply
need to increase the percentage of protein
in his diet from 15 to 21%. That way, he’ll hit
his protein target (135 grams) and his energy
needs (2,550 kcal) at the same time. Cutting
out ultra-processed foods and upping fibre
intake are simple ways to help concentrate
protein in his diet up to 21%, but increasing
the portion sizes of protein-rich foods to add
an extra 20 to 30grams of protein each day
to his diet would also help him get there.
Simple.
It has hardly been true for most of the
time our species has existed, but today,
losing a bit of weight is a goal many of
us share. Losing it is tough enough, but
keeping it off is harder still. The yo-yo
effect is all too common – lose weight by
going on the latest fad diet, bounce back
to the previous weight, or even worse,
put on more. It’s a terrific business model
for the weight-loss industry, and the
combination of our biology and modern
food environment makes it near inevitable.
Working with protein leverage can help. There is evidence from
large-scale clinical trials, such as the European DIOGENES study,
that a higher-protein diet (25%) coupled with lots of healthy, slowly
digested carbs helps keep weight off after a period on a low-calorie
diet (800 kcal per day for 8 weeks in the case of that particular study).
However, a common rookie error is to look at the health benefits
of a higher-protein diet and credit protein itself. Here’s how the
flawed logic goes: you lose weight on a high-protein diet; upon losing
weight, your health improves; therefore, protein improves our health.
But protein isn’t a medicine for fixing diabetes, heart disease, and the
other complications of obesity. As we now know, eating a diet with a
high concentration of protein simply provides a limit on total calorie
intake. Many benefits follow from that alone.
But today, there is a fad diet community that believes ‘if some
protein is good, more must be better.’ Another common error of
logic. It’s as false as saying that more of any good thing should be
better than precisely the right amount. There are plenty of beneficial
substances – salt, water, vitamins – that are toxic at too-high levels.
The same is true for protein, as well as carbohydrates and fats.
The high-protein dietary philosophy has been in vogue for some
time now. It was popularised in the works of Robert Atkins, who
recommended a low-carb, high-fat, high-protein diet to achieve
weight loss. He was right, and now we all know why – on such a
diet, you eat less overall because you have focused on fulfilling the
protein appetite. In the wake of Atkins came the popularity of paleo,
ketogenic, carnivory, other low-carb and even zero-carb diets that
advise eating nothing but meat, fish, eggs, butter (and maybe a little
fiber among the more cautious) for effortless weight control and
robust, animal good health.
Without fail, these will all stimulate weight loss. Added to the
hunger-busting effects of protein, the very low-carb keto regimen (on
which you’d eat less than 20 grams of carbs – the equivalent of an
apple a day) causes the body to burn ketones, which are breakdown
products of fat, as the main cellular fuel, rather than glucose. Ketones
also seem to help curb calorie intake, even when protein levels are
modest.
Low-protein (9%), very high-fat (90%) keto diets are therapeutic
in certain circumstances, such as for the treatment of epilepsy in
children; and very low-carb, low-energy diets can help reverse the
symptoms of type 2 diabetes; but neither is sustainable nor desirable
for most of us as a regular diet. Even somewhat less extreme lowcarb,
high-fat diets have low compliance – most of us soon drift back
to a more balanced mixture of macronutrients.
The reason is simple – if you remove most carbs from the diet,
you activate the carbohydrate appetite, which will make starchy and
sweet foods fabulously desirable. Try cutting carbs for a few days
and see. If your diet is also low in protein, then you will get the double
whammy of protein and carb cravings, along with the increasing
desire never to see fat again, as your appetite for that nutrient tells
you to stop eating it. Your appetites are simply doing what they have
evolved to do – trying their best to guide you to a balanced diet.
If you persist on a low-carb (or any extreme) diet, against all the
urges to do otherwise, your body will eventually adapt to it. We are
an extraordinarily flexible creature when it comes to diet. It’s been a
hallmark of our success as a species that we’ve been able to adapt
to diets as unpromising as those of the traditional Inuit (based on fish
and the meat and blubber of mammals), the Masai of Kenya (milk
and blood), or the Okinawans’ low-protein, sweet potato-based fare.
There is a downside, however – the more you restrict your nutrient
choices, the more you risk losing metabolic flexibility and will find
it difficult to shift to a different dietary pattern. This is because our
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