100
VOLUME 10 NUMBER 3 • SEPTEMBER 2013
REVIEW
SA JOURNAL OF DIABETES & VASCULAR DISEASE
Intermittent fasting: a dietary intervention for prevention
of diabetes and cardiovascular disease?
James E Brown,Michael Mosley, Sarah Aldred
Abstract
Intermittent fasting, in which individuals fast on consecutive
or alternate days, has been reported to facilitate weight loss
and improve cardiovascular risk. This review evaluates the
various approaches to intermittent fasting and examines the
advantages and limitations for use of this approach in the
treatment of obesity and type 2 diabetes.
Keywords
: diet, fasting, intermittent fasting, obesity, type 2
diabetes, weight loss
Introduction
The increasing prevalence of obesity and type 2 diabetes in recent
decades has been associated with increased comorbidities including
atherosclerotic macrovascular disease and premature mortality.
1–3
Individuals with sub-diabetic degrees of hyperglycaemia, such as
impaired glucose tolerance (IGT) and impaired fasting glucose
(IFG) are also at increased risk of premature cardiovascular disease,
emphasising the importance of interventions to improve glucose
homeostasis in pre-diabetic, as well as diabetic individuals.
4–5
Several large studies have identified pre-diabetic individuals
as subjects in whom to investigate lifestyle changes to prevent
the progression to a fulminant diabetic state.
6–10
However, there
is considerable debate regarding the most effective manner in
which lifestyle changes such as diet and/or exercise should be
implemented.
11
The approach of intermittent fasting is currently
generating particular interest.
Intermittent fasting
Extensive evidence suggests that imposing fasting periods upon
experimental laboratory animals increases longevity, improves health
and reduces disease, including such diverse morbidities as cancer,
12,13
neurological disorders
14-17
and disorders of circadian rhythm.
18,19
The
specific benefit of intermittent fasting as a health-giving therapeutic
approach has been recognised since the 1940s.
20
Correspondence to: Dr James E Brown
Aston Research Centre for Healthy Ageing and School of Life and Health
Sciences, Aston University, Birmingham, B4 7ET, UK.
e-mail:
Michael Mosley
Aston Research Centre for Healthy Ageing & School of Life and Health
Sciences, Aston University, Birmingham, UK
Sarah Aldred
School of Sport and Exercise Sciences, College of Life and Environmental
Sciences, University of Birmingham, UK
Originally in:
Br J Diabetes Vasc Dis
2013;
13
(2): 68–72
S Afr J Diabetes Vasc Dis
2013;
10
: 100–102
Intermittent fasting can be undertaken in several ways but
the basic format alternates days of ‘normal’ calorie consumption
with days when calorie consumption is severely restricted. This
can either be done on an alternating day basis, or more recently a
5:2 strategy has been developed (Figure 1), where two days each
week are classed as ‘fasting days’ (with < 600 calories consumed
for men, < 500 for women). Importantly, this type of intermittent
fasting has been shown to be similarly effective or more effective
than continuous modest calorie restriction with regard to weight
loss, improved insulin sensitivity and other health biomarkers.
1,21
Fasting has been used in religion for centuries. For example, the
Daniel fast is a biblical partial fast that is typically undertaken for
three weeks, and during Ramadan, the ninth month of the Muslim
calendar, there is a month of fasting during daylight hours, during
which some observers also refrain from fluid consumption.
22
Such
periods of fasting can limit inflammation,
23
improve circulating
glucose and lipid levels
24–27
and reduce blood pressure,
28
even when
total calorie intake per day does not change, or is only slightly
reduced. Ethical and logistical constraints have restrictedmost caloric
deprivation studies to six months, although some have assessed the
effects for longer.
29–31
The majority of studies show positive effects
on markers of metabolic health and body composition, in part due
to the demonstrated effects intermittent fasting has on metabolic
tissues (Figure 2). In addition caloric restriction studies undertaken
Figure 1.
Diagrammatic representation of a typical intermittent fasting plan.
Subjects who undertake this form of diet are required to limit their calorie intake
for two days, consecutively or otherwise each week. The calorie limit for fast-
ing days is approximately 25% of TDEE or 600 calories for men and 500 for
women. On non-fasting days subjects can eat normally to their TDEE calorie level
(approximately 2 500 for men and 2 000 for women).
Day 1
Normal
TDEE
Day 2
Normal
TDEE
Day 3
Fasting
500 (female)
600 (male)
Day 4
Normal
TDEE
Day 5
Fasting
500 (female)
600 (male)
Day 6
Normal
TDEE
Day 7
Normal
TDEE
Calories (per day)
TDEE = total daily energy expenditure
Figure 2.
Tissue-specific effects of intermittent fasting and calorie restriction.
Research has identified several biological effects of intermittent fasting and/or
calorie restriction on tissues that are central to metabolic and cardiovascular
health. NO: nitric oxide, TAG: triacylglycerides.
Fasting/calorie restriction
Liver
i
Fatty liver
h
Insulin
sensitivity
Blood vessels
h
No
i
Oxidative
stress
Adipose
tissue
h
Tag deposition
h
Insulin sensitivity
Pancreatic
islet
i
Age related
decline
Skeletal
muscle
h
Glucose
uptake
i
Insulin
resistance
