promoting diet-induced thermogenesis. The
old urban legend that the energy expended
in eating celery burns more calories than
there are in celery has some legs. The basic
ratio is 10-90: the brain triggers 10% of the
calories ingested to be burnt just to prime
the pump, to get at the remaining 90%. But
without that brain primer, such as when
people are tube-fed, that thermogenesis can
fall by more than 50%. Greger says it’s now
known that eating slowly and chewing a
lot optimises thermogenesis in a meaning-
ful way for weight loss. It may only be a
few extra calories pre-burnt per meal, but
it soon adds up.
WATER POWER AND GUT HEALTH
Water content is another aid to all this.
Drinking water with food doesn’t seem to
reduce food intake, but eating food with
a high water content does. That’s because
the food takes longer for the stomach to
deal with. It has to sieve, whereas with the
separate drink of water, it can simply syphon
the liquid off.
Repeated studies have shown that people
are less hungry hours after a meal whose
ingredients were liquidised into a thick or
chunky soup than the same ingredients – for
example, chicken and vegetables – in solid
form. The proviso remains, the slower the
ingestion the more powerful and lasting the
satiety.
But perhaps the biggest new fron-
tier in health and optimal weight is the
microbiome. Greger calls our gut bacteria
“our tenants ... It’s very exciting. We’re find-
ing out more all the time about the effect gut
bacteria have on our health. This research
has really improved our understanding,
especially of the value of eating whole-plant-
based foods.”
He looks forward to refining and updating
his body of work as more genetic research
comes out.Despite the attendant hype and market-
ing, reputable experts chime with Greger
that gut health is not just a craze but a
great leap forward. For a change, the sci-
ence is such that the concept of healthy
bacteria has rapidly gone mainstream – and
commercial.
Products claiming to galvanise gut health
now abound, from traditional food prepa-
rations such as fermented Korean kimchi
and drinks such as kombucha to Symprove,
a probiotic feed developed by a farmer for
his cows and later adapted for human
use. Yogurt products positively rejoice in
their “healthy bacteria” count, with muchpositive research data on traditional “bugs”
used to make kefir and Greek yogurt.
But like Greger, many highly qualified
experts say gut health can be achieved with-
out recourse to expensive new additives and
boutique foods.
Megan Rossi, an Australian-born con-
sultant with a doctorate in kidney disease
and gut health, says we need to be far more
ambitious about the diversity of plants we
eat. Five a day is not even close. As she told
the Times newspaper last year, “You need
to be eating 30 different types of plant-
based foods every week. Diversity is king,
because every fruit and vegetable, however
superficially similar – say, red and yellow
peppers – contains slightly different fibres
and chemicals that appeal to slightly dif-
ferent bacteria in your gut.”
She is, professionally, also a fan of kefir,
but like Greger’s, her patients are told that
optimising plant intake, in maximum vari-
ety, is ground zero for health.
Singing from the same hymn sheet is
also Andrew Jenkinson, consultant bariat-
ric surgeon at University College London
Hospitals and author of the book Why We
Eat (Too Much). Ditching refined foods and
tweaking the metabolism are features of his
charter.
Greger’s book is much fatter, but his head-
line message is blunter. “Don’t diet. Eat.”
He also has the satisfaction of disproving
an apparent oxymoron: the evidence-based
diet book does exist. lThe anti-fat message
seems simply to have
helped create an impliedlicence to eat more
low-fat food as well.