Should you try intermittent fasting? The evidence.

Home / Health / Should you try intermittent fasting? The evidence.

Have you ever wanted to:

– Do a lot less cooking and cleaning?
– Lose weight without starvation?
– Spend less on food?
– Target belly fat reduction?

Then intermittent fasting may work for you!

For most people, the call to try intermittent fasting comes from the desire to lose weight. While
this may be the most recognised benefit of the diet, or more so, eating routine, there are other
benefits too.

Intermittent fasting (IF) is a type of eating pattern that requires you to skip one or more meals for
a particular amount of time. Skipping meals allows you to automatically “cut calories”, giving you
a calorie deficit that allows you to eat relatively freely at your other meal times.

No calorie counting, macros or points to calculate. Plus you get the freedom to dine out and
choose whatever you wish to eat. These factors alone tend to be one of the key reasons why IF
is becoming increasingly popular.

Here, I discuss the evidence around both intermittent fasting for weight loss, other potential
benefits, some precautions and of course, how to get started.

INTERMITTENT FASTING WEIGHT LOSS BENEFITS

As mentioned, the key reason people try IF is for weight loss and losing belly fat (1).

IF is no different to other diets as it works by reducing your total calorie intake. So you burn
more than you consume, and ultimately, lose weight (2).

When you skip entire meals, you quickly reduce your daily calorie intake.

For example, an average woman typically aims for 1600-1800 calories a day as part of a weight
loss plan.

Skipping breakfast can save roughly 300-500 calories, leaving you with more calories to
consume in the meals you do eat while still staying on track with your weight loss goals.

In one study, one type of IF resulted in an average of 3.8kg more fat loss, compared to a very
low calorie diet (800 calories or less)(3).

Another study found IF helped reduce harmful belly fat with a reduction in participants’ waist
circumferences by 4-7% in 24 weeks (4).

In typical calorie restricted diets, researchers found that 25% of what weight you lose tends to
be muscle mass. However, only 10% muscle mass was lost using IF (5). This does depend on
how much protein you consume on your non-fasting days. It seems you need to eat 1.2 g of
protein/kg of body weight on non-fasting days to preserve fat-free muscle mass (6).

Another reason why IF may be superior to regular calorie restricted diets or other weight loss
methods is that it doesn’t send your hunger hormones crazy (7). A calorie restriction of 24 hours
or less isn’t severe enough to have you racing for that pack of chips or lollies for that
post-starvation, hormone-driven pick-me-up.

So when you fast in intervals that are shorter than 24 hours, you’re less likely to end up yo-yo
dieting and sabotaging yourself by overeating at your next meal. Ultimately leading to better
chances of you sticking to your lower calorie diet without feeling famished.

Your basal metabolic rate (the rate in which you burn energy simply by being alive) may also
increase post-fast. Researchers believe this is likely due to an increase of norepinephrine (as a
result of lower blood sugar during the fast). This rise in norepinephrine also increased fat
metabolism, meaning fat became the preferred fuel source of the body (8).

However, these effects don’t last if you continue to fast for longer than 3 days. In fact, your
basal metabolic rate can drop significantly.

OTHER BENEFITS OF INTERMITTENT FASTING

Fasting, in its many forms, has been a part of many cultures for years, including major religions –
Islam, Christianity and Buddhism.

Now, research is beginning to show that fasting can benefit more than just your waistline.

In fact, fasting has been shown to help positively influence key risk factors for disease, reduce
oxidative stress on your body, influence blood sugar levels, reduce inflammation, support a
healthy heart, and even preserve brain function including learning and memory.

REDUCE YOUR RISK OF CHRONIC DISEASE

Inflammation is a risk factor for most chronic diseases including heart disease, diabetes, obesity
and cancer (9).

Fasting increases your levels of human growth hormone and reduces inflammatory markers,
helping to initiate the processes that allow your body’s cells to repair.

In one study, inflammatory markers were reduced when the participants ate less than 30% of
their total daily intake in the evening and fasted for longer overnight periods than other study
participants. (10)

IF may also support a healthy heart by positively influencing your cholesterol levels and other
risk factors for heart disease. One particular study showed fasting resulted in increased HDL
cholesterol and decreased LDL cholesterol and triglyceride levels. (11).

Plus, according to one study, fasting may decrease blood sugar by up to 12% and lower insulin
levels by around 53% when you fast for around 16 hours daily (12).

BRAIN HEALTH

There is still a lot of research to be done in this area, but preliminary animal studies suggest that
IF may help enhance brain function, influence proteins involved in brain ageing and protect
against memory problems and Alzheimer’s disease (13,14,15).

How it does this isn’t yet quite understood, however, IF can increase a hormone called
brain-derived neurotrophic factor (BDNF) and may support the growth of healthy new nerve
cells (16).

More human research is needed to determine the full effects of IF, however, the existing studies
do show promising evidence to support the positive effects of fasting and its potential to reduce
our risk of chronic disease.

Types of Intermittent Fasting

How you fast is really up to you. For some, fasting for whole days is more appealing than simply
skipping one meal a day.

These are some of the types of intermittent fasting that you can follow:
The 5:2 Diet: ​Eat normally for 5 days of the week, but only eat up to 600 calories on the
other two days.
Eat-Stop-Eat or Spontaneous Fasting:​ Fast for a 12 or 24 hour period multiple times
per week. There is no real schedule for this one.
Alternate Day Fasting: ​Fast for one day and eat normally the next day. Continue to
alternate days of fasting and normal eating.
The 16/8 or Leangains Method:​ Fast for 16 hours per day and eat in the remaining
8-hour window. Most people will skip breakfast and eat from 1pm to 9pm for example.
Spontaneous Meal Skipping: ​Skip meals when convenient. Simply skip 1 or 2 meals
when you don’t feel hungry or don’t have time to eat.

Precautions

Despite the potential benefits of IF, it’s always best to speak to your health practitioner before
trialling any new health or diet regime.

For some people, fasting can be harmful to their health depending on their current health status.
Fasting may not be right for you if you have one or more of the following:

● Low blood sugar levels
● History of eating disorders
● Women with long-term hormonal issues or amenorrhea
● Gallstones
● Thyroid issues

Pregnant women and those who are sick or ill should also avoid IF and focus on eating regular
healthy meals to nourish the body.

Whether you choose to fast for just a few hours each day, skip an entire meal, or fast for two
days a week, the benefits of intermittent fasting are continuing to surface, and thanks to its
adaptability to most lifestyles, it may well be one of the easiest ways to maintain a healthy
weight and reduce your risk of a variety of chronic diseases.

Larina Robinson

Larina Robinson is a Wholefood Dietitian, author and founder of The Body Dietetics. Specialising in gut health, food intolerances and alternative diets, Larina empowers people to embrace a diet unique to their own dietary needs and supports them to find freedom from long-term digestive complaints.

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