YMCA Healthy Living Magazine, powered by n4 food and health Winter 2019 | Page 8

CATHERINE SAXELBY, APD
Catherine is an Accredited Practising Dietitian and Nutritionist who has researched
and written on almost all aspects of healthy eating. Her skill lies in translating
scientific research into real nutrition terms. Catherine is the author of 12 books
including her Complete Food and Nutrition Companion (Hardie Grant). She also runs
the Foodwatch website, offering nutrition information for consumers (www.
foodwatch.com.au)
LOW CARB,
HIGH FAT DIETS:
ARE THEY SAFE
AND DO THEY
ACTUALLY WORK?
Exploring the safety and effectiveness of the ketogenic diet craze,
with Catherine Saxelby.
LOW-FAT
VS LOW-
CARB
In 2018, researchers at Stanford
University published the findings of
their DIETFITS Randomised Clinical
Trial (RCT) involving 609 overweight
adults. They were interested in
whether gene patterns or insulin
secretion seemed to affect weight
loss, or predict who did better on the
two diets.
Participants were split into two groups,
with half following a healthy low-fat diet
and the other half, a healthy low-carb
diet. At 12 months, they were weighed
and any changes noted.
The results
n recent years low carb, high
fat (or ‘ketogenic’) diets have
gained a lot of air time and
popularity. Low carb devotees will tell
you it’s the best way to eat for weight
loss, and that it’s more of a healthy
lifestyle than a diet. We asked one of
Australia’s favourite nutritionists –
Catherine Saxelby – for her thoughts
on the safety and effectiveness of low
carb diets.
I
First things first, what are
carbohydrates, and what does
a low carb diet look like?
Carbohydrates are one of the main
sources of fuel in our diet. They break
down to glucose in our blood, which
may then be either used for energy, or
stored by the body (sometimes as fat).
Carbohydrate foods include fruit,
starchy vegetables, cereals/grains (e.g.
bread, breakfast cereal, pasta) and
legumes. Refined sugars used to
sweeten foods, such as sucrose (table
sugar) and honey are also carbohydrates.
8
Even milk contains a natural carbohydrate
called lactose.
Low carb diets either omit or drastically
reduce the food groups above. And when
the body is starved of carbohydrate, it
must use alternate sources of fuel.
Essentially, ketosis (the goal of low carb
diets) means our bodies run out of
glucose, and are forced to produce an
alternate source of energy – ketones –
for fuel. This usually involves the
breakdown of body fat and muscle, in
order to keep us alive.
Sounds drastic, doesn’t it? It also
sounds like a good way to shed weight
quickly. But does it actually live up to
all the hype, and does it cause
sustained weight loss? Let’s weigh up
the impact of a low-carb diet versus a
low-fat diet on overweight adults (see
red box on the right).
What does the science mean?
What you need, and what I’ve always
advocated, is an all-round healthy diet.
YMCA HEALTHY LIVING MAGAZINE WINTER 2019
After 12 months, the group on the
low-fat diet had lost on average 5.3kg
and the low-carb group, 6kg. Not the
huge difference often spruiked by
advocates for one or the other regime,
and not a clinically significant
difference in scientific terms!
Of note: both groups in this study
were asked to kick off with a very low
level of either carbohydrate (less than
50g per day) or fat (less than 20g per
day). And neither group was able to
maintain this very low level for the
required two months! Both the very
low-fat and the very low-carb diets
were unsustainable – something
dietitians have been saying for ages!
This study did not show any significant
relationship between genetic makeup
or insulin levels, and ability to lose
weight. In other words, these factors
didn’t give us any additional insight
into which people would succeed on
either diet.