Intermittent fasting – fad or fab? - Register of Exercise Professionals

Intermittent fasting – fad or fab?
• Understand what intermittent fasting is and its
claims
• Outline a range of intermittent fasting diets
• Review the research around intermittent fasting
• Describe the risks and limitations of intermittent
fasting
• Understand the implications of exercising whilst
in a fasted state
• Be able to give appropriate advice to clients
wanting to start intermittent fasting diets
Vicky Tester
• Resource and Accreditation Manager for the
fitness sector of Lifetime Training Group
The claims of intermittent fasting diets
Lose weight quicker and
easier than before!!
Switch on your biological powerhouse for high
energy, explosive strength and a leaner, harder body!!
Turn on your skinny gene, shed the pounds
and live a longer and healthier life!!
Lose more weight and twice as much fat as a
standard calorie controlled diets and keep it off!!
Intermittent fasting (IF): Definition
“A dieting pattern, with periods of
fasting and non-fasting”
Corrects metabolic abnormalities as well
as showing better adherence than other
traditional nutritional principles
Different types of IF diets
Eat stop
eat
5-2 fast
diet
Warrior
diet
Lean
gains
Alternate
day diet
5:2 fast diet:
• Diet for two consecutive days and eat normally for the rest
of the week
 Unrestricted days should eat normally
with little thought to calorie intake
• Only eat 500-600 calories on the fast day
• On the 2 days you are allowed food that are high in protein
and fibre as these are the most satiaiting
Warrior diet:
20 hour fast followed by a
4 hour feed
• Eat very small amounts for the first 18-20 hours of each day and
exercise during this period
• Under eating and short term fasting with exercise will improve insulin
sensitivity
• Consume the majority of daily calories within a 4-6 hour window
Lean gains
• 16 hour fast followed by an 8 hour feed
generally consisting of 3 meals
16 hour
fast
8 hour
feed
• On workout days there is an emphasis
on carbs, on rest days fat is prioritised,
protein intake remains high on all days
• Variety of protocols for when to
consume food and workout:
o e.g. workout is performed at the
end of the fast (consume 10 BCCA
prior)
EAT.....
…..EAT
• 24 hour fast, 1 or 2 two times per week & eat sensibly the rest of the week
• During a 24 hour fasting session there is an increase in growth hormone,
insulin levels are low, cortisol levels are balanced and the adrenal glands
function well
Alternate day diet
• Eat what you want one day then fast the next
• On the fast day eat a very restricted diet
(400kcal for women & 500kcal for men)
• Encouraged to make good eating choices but
allowed to eat what you want on non-fast
days
What does the research show?
• Animal models have shown positive changes in
glucose, lipid metabolism and increased
resistance to stress (Azevedo et al 2013)
• Following periods of between 16-24 weeks of
alternate diet fasting (ADF) reduction in heart
rate and fat levels found in studies on rats (Varady
et al 2009, Mager et al 2006 & Wan et al 2003)
Human studies of Intermittent Fasting
• Human studies show that ADF does not alter fasting concentrations of
glucose but can control other risk factors of diabetes, e.g. insulin
sensitivity (Varady 2007)
• Human subjects fasted on alternate days for 3 weeks HDL cholesterol
increased, triglycerides decreased (Heilbron et al 2005)
• Study to assess the cardiovascular health of Muslim individuals during
Ramadan showed improvements in lipid profile (Aksungar et al 2005)
More effective that calorie restricted (CR) diets?
Limitations
of IF
• The majority of the research has been conducted on animals
• Risk of type 2 diabetes has favourable alterations in animals but less
conclusive in humans
• Studies have lacked control groups and used short trial lengths
(Varady 2007)
• Restricting daily intake by 15-40% has been shown to improve
glucose tolerance and insulin action, reduce blood pressure and
heart rate, protect against oxidative stress and increase lifespan
(Review Varady et al 2007)
IF vs CR
• Decreases in heart rate and blood pressure induced by ADF were
similar to those induced by calorie restricted diets (Review Varady et al
2007)
• IF & ADF are equally as effective as calorie restricted diets for weight
loss and the prevention of coronary heart disease.
Exercising whilst in fasted state
Do you burn more fat?
• Rationale: Exercising with low glycogen levels will cause the body
to shift energy utilization away from carbohydrates allowing a
greater mobilisation of stored fat for fuel
• Inconclusive scientific research to support this theory.
• For significant changes in body composition fat oxidation should
be considered over the course of days and not a single workout
• Research supports that high intensity training is an effective
method for maximising fat loss
Increase risk of injury?
• Exercise in a fasted state vs fed state can decrease static and
dynamic balance which can increase the likelihood of injury
(Johnson & Leck 2010)
What should I be telling my clients?
Is IF suitable for me? No if any of the following………………
•
•
•
•
Need to closely monitor blood sugar levels
Are pregnant or breast feeding
Have a history of disordered eating or already underweight
Taking prescribed medication
Could IF work for you?
• YES. IF is an effective intervention for weight loss and will help reduce the risk of
cardiovascular disease but no more so than traditional calorie restricted diets
• Consider your lifestyle, work and family commitments before starting
Am I more likely to stick to an IF regimen than a calorie restricted one?
•Intermittent fasting regimens evolved to increase adherence to dietary restriction
methods
•85% adherence to a regimen of a fast day (25% of base line energy needs) followed by a
feed day
The downsides of IF
• Extreme hunger
• Increase irritability and changes in mood
• Develop unhealthy obsession with food
• Risk of over consumption on the non-fast
days
• Encourage an over reliance on caffeine on
the fasting days
Take home messages
•Research on the specific effects of IF is limited and still in its infancy with only a
handful of human studies under its belt
•Many variations of these diets exist because there is no one established method that
is best
•Most effective weight loss plans are those that are based on sound nutritional
principle and can be maintained
•If intermittent fasting is appealing to the individual trail for 2-3 weeks then evaluate
its effectiveness and whether or not it is a suitable, sustainable option for them
•There is a critical transition period of about 3-6 weeks during which the body and the
brain adapt to a new eating schedule (Longo and Mattson 2014)
•If fasting isn’t sustainable then still an effective tool for managing appetite
Questions