The New York Times International - 30.08.2019

THE NEW YORK TIMES INTERNATIONAL EDITION FRIDAY, AUGUST 30, 2019 | 7

well

Low-carbohydrate diets have fallen in
and out of favor since before the days of
Atkins. But now an even stricter version
of low-carb eating called the ketogenic
diet is gaining popular attention, ignit-
ing a fierce scientific debate about its po-
tential risks and benefits.
Both the Atkins and ketogenic diets
encourage followers to cut carbs from
their diets. But while the Atkins diet
gradually increases carbs over time,
keto places firm limits on carbs and pro-
tein. This way of eating depletes the
body of glucose, forcing it to primarily
burn fat and produce an alternate
source of fuel called ketones. A typical
ketogenic diet restricts carbs to less
than 10 percent of calories and limits
protein to 20 percent, while fat makes up
the rest.
The keto diet has been popularized in
best-selling books, promoted by celebri-
ties and touted on social media as an an-
tidote to various ailments. Proponents
say it causes substantial weight loss and
can help those with Type 2 diabetes dra-
matically improve their blood sugar lev-
els, which fall when people avoid carbs.
There have been many studies of the
ketogenic diet over the years, but most
have been small. A federal registry of
clinical research shows that more than
70 trials looking at the diet’s impact on
brain, cardiovascular and metabolic
health are either underway or in the be-
ginning stages.
Dr. Ethan Weiss, a researcher and
preventive cardiologist at the Univer-

sity of California, San Francisco, had

long been skeptical of low-carb diets but

decided to experiment with the ketogen-

ic diet a couple of years ago. In a typical

day, he skips breakfast and eats mostly

salads, nuts, cheese, roasted vegetables,

and grilled chicken, fish or tofu, as well

as dark chocolate for dessert. The re-

sult, he says: He lost 20 pounds and had

to buy a new wardrobe.

Dr. Weiss subsequently started a com-

pany and a weight loss app with a for-

mer Weight Watchers vice president,

raised $2.5 million from a group of Sili-

con Valley investors and started selling

a $99 pen-size breathalyzer device,

called Keyto, that allows users to meas-

ure their ketone levels and track how the

diet is working for them.

“Our mission is to make doing this

diet easier and more sustainable so peo-

ple can make changes that allow them to

lead a healthier lifestyle,” he said.

But the ketogenic diet has no shortage

of detractors. Some doctors and health

experts say it can lead to quick weight

loss but that it is no more effective than

other diets in the long term. And many

say they find it worrisome because it en-

courages foods high in saturated fat,

which have been linked to heart disease,

while restricting nutrient-rich foods

supported by decades of research, like

beans, fruits, starchy vegetables and

whole grains.

Last month, three doctors published

an essay in JAMA Internal Medicine

cautioning that the enthusiasm for the

diet as a treatment for obesity and dia-

betes “outpaces” the evidence. They

pointed to studies suggesting that it had

little advantage over lower-fat diets for

blood sugar control, and that it could

cause adverse effects like constipation,

fatigue and, in some people, an increase

in LDL cholesterol particles, a risk fac-

tor for heart disease. “The greatest risk,

however, of the ketogenic diet may be

the one most overlooked: the opportuni-

ty cost of not eating high-fiber, unrefined

carbohydrates,” the authors wrote.

“Whole grains, fruits and legumes are

some of the most health-promoting

foods on the planet. They are not respon-

sible for the epidemics of Type 2 diabe-

tes or obesity, and their avoidance may

do harm.”

Dr. Shivam Joshi, a co-author of the

essay, said it generated a flood of emails

from people across the globe. Some ex-

pressed praise and support, while oth-

ers offered condemnation, a sign of just

how polarizing the diet can be, said Dr.

Joshi, an attending physician at NYC

Health + Hospitals/Bellevue and a clini-

cal assistant professor at New York Uni-

versity medical school.

While the ketogenic diet can seem like

the latest in a stream of fad diets, it has a

long history of therapeutic uses. Diabet-

ics routinely practiced carb restriction

before the discovery of insulin in the

1920s, and doctors at Johns Hopkins and

other hospitals have used the diet for al-

most a century to reduce seizures in pa-

tients with epilepsy.

One of the benefits of carb restriction

is that blood sugar levels remain stable

after a meal, resulting in lower levels of

insulin, a hormone that causes weight

gain, said Dr. David Ludwig, an endocri-

nologist at Harvard Medical School and

the author of a best-selling book on low-

carb diets.

“Insulin is like a Miracle-Gro for fat

cells,” he said. “By lowering insulin lev-

els, fewer calories from the meal may

get stored in fat cells, leaving more to

fuel metabolism and feed the brain. As a

result, you may feel fuller longer after

eating.”

In a series of studies over the years,

Dr. Ludwig has found that low-carb diets

cause people to burn more calories and

lose more weight compared with lower

fat diets. According to the carb and insu-

lin theory of obesity, whole grains,

starchy vegetables and tropical fruits

are more healthful than processed

carbs. But they can still cause swings in

blood sugar and insulin after a meal, and

that can be particularly problematic for

people with diabetes, said Dr. Ludwig.

In May, the American Diabetes Asso-

ciation published a consensus state-

ment on nutrition strategies for people

with diabetes. It found that a variety of

diets rich in unprocessed foods, like the

Mediterranean and vegetarian diets,

could help people prevent and manage

the disease. But it also concluded that

reducing overall carb intake “has dem-

onstrated the most evidence” for im-

proving blood sugar control.

“Carbohydrate is the macronutrient

that most contributes to your blood sug-

ar, and so it makes sense that reducing it

is going to give you the biggest bang for

your buck,” said the lead author of the

report, Dr. William S. Yancy Jr., an asso-

ciate professor at Duke medical school

and the director of the Duke Diet and

Fitness Center.

But the carb and insulin explanation

for obesity is the subject of much debate.

Scientists at the National Institutes of

Health have published research show-

ing that people actually burn more calo-

ries on low-fat diets, and many experts

contend that in the end, people will lose

weight on any diet so long as they con-

sume fewer calories.

The ketogenic diet has been touted on social media as an antidote to various ailments. Proponents say it can help people with Type 2 diabetes because of the strict limits on carbs.

MARIA AMASANTI FOR THE NEW YORK TIMES

Even tighter limits on carbs

Ketogenic diet can lead

to weight loss, but doctors

are divided on its effects

BY ANAHAD O’CONNOR

A flood of emails showed how

polarizing the diet can be.

Lately, at airport gates and security

lines, I’m increasingly hearing other fre-

quent fliers share stories of spilled cof-

fee and sudden drops on planes.

Threaded through nearly every conver-

sation are questions about whether

there has been an upswing in air turbu-

lence and whether climate change is to

blame.

Turbulence has never been a concern

for Ashwin Fernandes, who takes more

than 200 flights per year as regional di-

rector to the Middle East, North Africa

and South Asia for Quacquarelli Sy-

monds (QS) World University Rank-

ings, until a bad flight in 2013 left him

spooked.

“We were over the Bay of Bengal dur-

ing monsoon season and the plane

started shaking violently and then

dropped suddenly,” he recounts. “I did-

n’t know what to do, except wonder how

much worse it would get and when it

would end.”

Since then, Mr. Fernandes has fol-

lowed a strict set of self-imposed rules,

which includes taking daytime flights

whenever possible. Red-eye flights, he

says, can be more anxiety-provoking be-

cause of fatigue. But one question con-

tinues to haunt him: Is global warming

making the skies less friendly?

Maybe, but only at certain altitudes,

said Paul D. Williams, professor of at-

mospheric science at the University of

Reading, who is the co-developer of a

turbulence-forecasting algorithm that

has helped make flight travel more com-

fortable by avoiding rough air and

greener by reducing carbon dioxide

emissions via “low turbulence” routes.

“Climate change is altering tempera-

ture patterns and wind speeds in the up-

per atmosphere,” he said. “The main

consequence for aviation is an increase

in clear-air turbulence, or in-flight

bumpiness at high altitudes in regions

devoid of significant cloudiness or

nearby thunderstorms, as the jet stream

becomes more unstable.”

But severe turbulence, the kind that

causes passengers who aren’t wearing

their seatbelts to defy gravity and lift up

from their seats, remains a very rare oc-

currence.

“Only around 0.1 percent of the atmos-

phere at flight cruising levels contains

severe turbulence, so even if that figure

were to double or treble because of cli-

mate change, severe turbulence will still

be very rare,” Dr. Williams said. Offering

grounds for optimism, he added, “Hope-

fully, a combination of improved turbu-

lence forecasts and better technology

will reduce the number of aircraft en-

countering turbulence in the future, de-

spite the effects of climate change.”

The takeaway is to remain buckled

throughout the flight, as is routinely in-

structed by the cockpit crew before

takeoff. Airlines want passengers to be

comfortable throughout the journey,

which is the main reason for avoiding

turbulence. Cargo planes, filled with

packages instead of people, on the other

hand, tend to stay the course even when

the air is rough.

“No matter how scary it might feel,

our pilots are in control and there is no

question of structural integrity,” said

Rich Terry, a captain and managing di-

rector of fleet support for Delta Air

Lines. “Modern aircraft are developed

and tested to sustain any level of con-

ceivable turbulence.”

Mr. Terry said the easiest way to

make sense of turbulence is to think

about ocean waves cresting and falling.

“That same movement happens in the

air, so now picture those same move-

ments throughout the atmosphere.

When airplanes intersect those waves,

you have turbulence.”

In other words, it’s a natural occur-

rence and should be expected — not

dreaded. Learn to go with the flow.

“Expect, accept, allow” is the self-reg-

ulating advice offered by Martin N. Seif,

a psychologist with private practices in

New York and Connecticut who co-

founded the Anxiety and Depression As-

sociation of America and is a co-author

of “What Every Therapist Needs to

Know About Anxiety Disorders” and

“Overcoming Unwanted Intrusive

Thoughts.”

When experiencing turbulence, Dr.

Seif suggested replacing “what if”

thoughts with “what is” thoughts. “Stay

present,” he advised. “Anxiety is fueled

by catastrophic thoughts and is main-

tained by attempts to avoid it.”

Ashley Nicholls, who frequently flies

around the Northeast with her Vermont-

based marketing and communications

firm, said that when the going gets

rough, she distracts herself with math —

subtracting from 100 by threes. “By the

time I get to 1, the bumps are done. If

they aren’t, I start over.”

Adam Bluestein, a freelance journal-

ist, grew weary of his worries over

weather and decided to rewrite the

script in his head. Previously reliant on

an array of spiritual talismans — a

Ganesh necklace, a tiny Buddha statue,

a pouch of crystals, and 36 cents

wrapped in a piece of aluminum foil as a

Jewish blessing for life — Mr. Bluestein

found a better way to check in and zone

out.

He embarked on a cognitive behavior-

al therapy of his own design, which in-

cluded educating himself in the laws of

space and physics, and then flying to

Thailand to re-establish his sense of

courage.

The outcome was a complete reset of

his mental state. He no longer obsesses

about what’s out of his control. Letting

go, he learned, is the biggest obstacle for

anxious fliers.

“Now I go up with a calmer state of

mind. I observe what’s happening, I

don’t react. When I see the wings bend, I

know that’s what they are meant to do,”

he said, also crediting yoga for helping

him “muster of a sense of detachment”

even in turbulence.

Just stay buckled up:

The bumps will pass

Turbulence is natural,

so experts suggest you

learn to go with the flow

BY NANCY STEARNS BERCAW

A United Airlines service manager

giving safety instructions to a

plane full of passengers.

JULIO CORTEZ/ASSOCIATED PRESS

For women with serious depression, a
single session of exercise can change
the body and mind in ways that might
help to combat depression over time,
according to a new study of workouts
and moods. Interestingly, though, the
beneficial effects of exercise may
depend to a surprising extent on
whether someone exercises at her own
pace or gets coaching from someone
else.
Already, a wealth of recent research
tells us that exercise buoys moods.
Multiple studies show that physically
active people are more apt to report
being happy than sedentary people
and are less likely to experience anxi-
ety or depression. In a few experi-
ments, regular exercise reduced the
symptoms of depression as effectively
as antidepressant medications.
But science has yet to explain how
exercise, a physical activity, alters
people’s psychological health. Many
exercise scientists speculate that work-
ing out causes the release of various
proteins and other biochemical sub-
stances throughout our bodies. These
substances can enter the bloodstream,
travel to our brains and most likely
jump-start neural processes there that
affect how we feel emotionally.
But it has not been clear which of
the many substances released during
exercise matter most for mental health
and which kinds of exercise prompt the
greatest gush in those biochemicals.
Those open questions prompted

Jacob Meyer, an assistant professor of

kinesiology at Iowa State University in

Ames, to start considering endo-

cannabinoids and the runner’s high.

As the name indicates, endocannabi-

noids are self-produced psychoactive

substances, similar to the psychoactive

compounds in cannabis, or marijuana.

Created in many of our body’s tissues

all the time, endocannabinoids bind to

specialized receptors in our brains and

nervous systems and help to increase

calm and improve moods, among other

effects.

Past studies show that exercise often

increases the levels of endocannabi-

noids in the bloodstream, probably

contributing to the so-called runner’s

high that leaves some people feeling

tranquil and floaty after workouts.

At the same time, problems with the

endocannabinoid system are linked

with some mental health concerns.

People with diagnoses of depression

often have relatively low levels of

endocannabinoids in their blood, for

instance, while mice and rats born with

malfunctioning endocannabinoid re-

ceptors typically develop a kind of

rodent depression.

So, Dr. Meyer thought, might exer-

cise that increases endocannabinoid

levels potentially play a role in combat-

ing depression? And if so, what kinds

of exercise would produce such an

increase, and what kinds would not?

To learn more, Dr. Meyer turned to

stored blood samples and other

records from a relevant earlier experi-

ment. That research, which he had

conducted as a doctoral student at the

University of Wisconsin, had involved

women with major depression com-

pleting a number of workouts on sta-

tionary bicycles.

Each of the workouts lasted for 20

minutes, but their intensities varied

substantially, from light to draining.

During most of the sessions, the wom-

en were told how intensely to pedal,

with their efforts monitored and ad-

justed so they maintained that level.

But during one workout, they could

choose the intensity, pedaling as easily

or strenuously as they liked.

Before each session, the women

gave blood and completed question-

naires about their emotional states.

Immediately afterward, they gave

blood again and, 10 minutes and 30

minutes later, repeated the question-

naires.

In earlier studies using data from

this experiment, Dr. Meyer reported

that any exercise, whether its intensity

was light or difficult, left the exercisers

feeling more cheerful. However, the

positive impacts tended to be more

substantial when the women followed

directions about how intensely to

exercise compared to when they set

their own pace.

Now, for the new study, recently

published online in Medicine & Science

in Sports & Exercise, Dr. Meyer set out

to see if any changes in the women’s

endocannabinoid levels after the differ-

ent sessions might have played into

that dynamic. For the sake of a simple

comparison, he focused on one session

in which the women had cycled contin-

uously at a moderate pace and another

in which they had pedaled at whatever

intensity they chose. For most, their

you-pick effort was gentle; but for

others, it was moderate, and for a few,

intense.

And he found notable differences in

outcomes. After both workouts, the

women reported feeling less depressed

and worried. But only when they had

followed instructions to pedal moder-

ately did their blood show increases in

endocannabinoids. When they had

exercised at their preferred pace, even

if it was moderate, endocannabinoid

levels remained unchanged.

What these results suggest, Dr.

Meyer says, is that being coached and

supervised leads to different impacts

on our bodies and minds than working

at our own pace, whatever that pace

might be.

Why the prescribed exercise should

have increased endocannabinoids

while the go-as-you-please workout did

not is still mysterious, he says. It may

be that our brains recognize when a

workout’s intensity is not one we

would voluntarily choose and prompt

the release of substances that make

the effort more tolerable. That idea

requires additional research, he says.

This study also did not look at men

with depression or the long-term im-

pacts of the exercise, and whether any

increases in endocannabinoids reduced

depression over time. In the short

term, both types of exercise made the

women a bit happier.

Over all, the study underscores that

our responses to exercise can be com-

plicated, interweaving the physiolog-

ical and the psychological, Dr. Meyer

says, but any exercise is better for

mental health than none.

“It might be helpful for people suf-

fering from depression to work with a

personal trainer or other fitness pro-

fessional” who can supervise the ses-

sions, he says.

But in the end, “for improving de-

pressed mood state, exercise of any

intensity appears helpful.”

Coaching may help exercise lift your mood

Fitness

GRETCHEN REYNOLDS

A new study suggests that supervision leads to different impacts on our bodies and minds than working at our own pace.

KENDRICK BRINSON FOR THE NEW YORK TIMES

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