1 January 2022 | New Scientist | 37for any weight-loss regime. As paradoxical
as it may seem, cultivating an indulgent
attitude to food may be the best way to
control your waistline.
It was a man called Henry Molaison
who provided some of the first clues to the
ways our mind can influence our appetite.
In the early 1950s, Molaison underwent
experimental brain surgery to treat epilepsy,
but the operation caused irretrievable
damage to his hippocampus. As a result,
he could no longer form new memories,
leading him to live in the “permanent
present tense”, in the words of the
neuroscientist Suzanne Corkin.
Observations of Molaison’s behaviour
helped to revolutionise our understanding
of memory. They revealed, for example, that
we can learn skills unconsciously without
being able to recall the lessons themselves.
Less well-known, however, is Molaison’s
seemingly bottomless stomach. In the 1980s,
Nancy Hebben at Harvard University asked
him to rate his satiation on a scale from 0
(famished) to 100 (completely full) before and
after his meals. If appetite were mostly directed
by signals from the stomach, you would have
expected Molaison’s ratings to have risen
after his meals. Yet they barely shifted.
To test whether his memory deficit would
change his eating behaviour, the scientists
performed a dinner-time experiment. After
he had finished his meal, they cleared the table,
and, within a minute, offered another plate
of food. Amazingly, he ate nearly all of it –
and, despite having consumed almostThe indulgence
effect
Changing the way we perceive healthy food may be the secret
to successful dieting, finds David Robson, thanks to an ironic
consequence of the mind-body connection
I
F YOU are craving a satisfying dish but
trying to be careful about your weight,
few things are more dispiriting than
reading the “healthy” options on a food
menu. Words like “light”, “wholesome”,
“skinnylicious”, “sensible”, “mild” – the
adjectives that often accompany low-fat,
low-carb options – hardly prepare you
for a pleasurable meal.
One obvious consequence is that it makes
the foods seem less desirable, so you may
be more tempted by indulgent choices: the
“rich”, “flavourful”, “delicious” dishes. But
the influence of these words can stretch far
beyond our immediate decision-making.
The way we think about food can powerfully
influence our satiety long after we have
finished eating, and thanks to the mind-body
connection, it can even shape our hormonal
responses and the meal’s passage through
the gut. As a result, our expectations
around food can determine whether we will
experience greater hunger pangs afterwards
and find it harder to resist snacking later
in the day. And this is all down to the sense
of deprivation created by the way the food
was described, irrespective of the number
of calories actually consumed.
No wonder dieting is often so agonising:
our culture has led us to associate healthy
eating with greater hunger, and that becomes
a self-fulfilling prophecy. Fortunately, as I
describe in my book The Expectation Effect,
there are many ways to change our food
mindsets, and they all centre on the idea
that pleasure is an essential ingredient >
twice as much as normal, he reported
only a moderate increase in his satiety.
How could this be? There is little doubt that
appetite is influenced by “bottom-up” signals
in the digestive system, such as a feeling of
stretch in the muscles of the gastrointestinal
tract, and feedback from chemical sensors
that can detect the presence of nutrients.
The experiences of people with amnesia like
Molaison, however, suggest that we also rely
on “top-down” sources of information – such
as our memories of what we have eaten – to
make sense of those cues, create the overall
feelings of satiety and hunger, and to control
subsequent food intake.
Amnesia may offer extreme examples of
these processes in action, but further research
has shown that we are all susceptible to top-
down influences on our appetite. Even mild
forgetfulness seems to increase someone’s
chances of overeating, while prompts to recall
a previous meal curb people’s snacking.
In one notable experiment, Suzanne Higgs
at the University of Birmingham, UK, invited
a group of students into her lab to perform
a taste test on some cookies, which, after
completing a couple of questionnaires, they
were free to consume. Higgs found that
prompting the subjects to remember their
lunch, by spending a few minutes describing
what they had eaten, caused them to eat about
45 per cent less – around four cookies – than
participants who wrote about their general
thoughts and feelings, rather than their meal
memory. This wasn’t the case for participants
who wrote about a meal from the day