VOLUME 10 NUMBER 3 • SEPTEMBER 2013
101
SA JOURNAL OF DIABETES & VASCULAR DISEASE
REVIEW
in animals and humans have suggested that fuel selection is altered
and efficiency of metabolism is improved
32,33
while oxidative stress
is reduced.
34
It is possible that short periods of fasting mobilise
ectopic triacylglyceride (TAG) in non-adipose depots, reducing
the detrimental effects of intra-myocellular and intra-hepatic TAG
deposition
19,35
and redistributing TAG into adipose tissue.
Intermittent fasting and obesity
Obesity comprises multiple genetic, metabolic and behavioural
abnormalities that complicate treatment. Most pharmaceutical
therapies that promote weight loss have been discontinued, and
at the time of writing the only licensed anti-obesity drug on the
UK market is orlistat.
1
Increasing numbers of obese individuals are
undergoing bariatric surgery, but this remains a restricted minority
treatment.
36
The mainstay of treatment for obesity therefore
remains lifestyle intervention based around dietary changes
37-40
which generally form the first step in any weight-loss programme.
Intermittent fasting is known to be useful in the treatment of
intractable obesity,
41
and morbidly obese individuals.
42
Original
treatment regimens were based upon intermittent starving as
opposed to restricting calories
43,44
a harsh regime that must have
challenged adherence. Despite the seemingly strict nature of the
fasting days, intermittent fasting has a generally good adherence
record and can cause significant reductions in body weight in
individuals with obesity,
45-46
suggesting that this is a clinically relevant
therapeutic approach.
Intermittent fasting and type 2 diabetes
Since obesity commonly co-exists with type 2 diabetes
1
patients are
usually initially assigned lifestyle interventions aimed at reducing
body weight.
46
Most obese type 2 diabetes patients however will
progress onto drug-based therapies, some of which can exacerbate
their existing obesity.
1
Intermittent fasting can reduce the incidence
of diabetes in experimental animals
47–49
and there is evidence that
this type of fasting may also slow the progression of type 2 diabetes
in obese individuals.
Indeed, a recent study confirmed earlier reports of a reversal of
type 2 diabetes through daily calorie restriction, with improvement
of pancreatic function and a reduction of occult triglyceride
deposition.
50
The particular diet employed a maximum of 600
calories every day, which may prove too severe for many type 2
diabetes patients, but an intermittent fasting strategy may be more
acceptable and still improve metabolic parameters, insulin levels
and insulin sensitivity
51,52
and prevent the development of diabetic
complications.
53
Indeed, intermittent fasting might achieve much
of the benefit seen with bariatric surgery,
65
but without the costs,
restriction on numbers and risks associated with surgery.
Whether intermittent fasting can be used as a tool to prevent
diabetes in those with IGT or IFG, or to prevent progression in those
recently diagnosed with type 2 diabetes remains a tantalising notion.
Intermittent fasting and cardiovascular disease
Although with up to 80% of obese type 2 diabetes patients die
from cardiovascular complications,
54,55
and the benefits of weight
loss are well recognised
56
it is also known to be more difficult for
individuals with type 2 diabetes to lose weight.
57,58
Intermittent represents a potential therapy for those at high
cardiovascular risk. Intermittent fasting in animal models can
reproduce some of the cardiovascular benefits such as improvements
in blood pressure and heart rate that are seen with physical
exercise.
59
Caloric restriction studies have shown improvements in
circulating cholesterol, triglycerides, improved blood pressure, and
reduced carotid intima–media thickness.
28,60
Also, improvements
in physiological cardiovascular parameters are associated with
intermittent fasting and survival from l myocardial ischaemia
61
through
pro-angiogenic, anti-apoptotic and anti-remodelling effects.
Intermittent fasting also appears to be cardioprotective, providing
experimental animals with resistance to ischaemic injury,
62
in a
manner possibly associated with increases in levels of the adipokine
adiponectin.
63
Adiponectin is a unique adipokine that appears to
have beneficial effects but has circulating levels that are negatively
correlated with body composition.
64,65
However, intermittent
fasting modulates the levels of visceral fat and several additional
adipokines, including leptin, interleukin-6 (IL-6), tumour necrosis
factor alpha (TNF-
α)
and IGF-1.
66
These changes are responsible
for a reduction in low-density lipoprotein cholesterol (LDL-C) and
total cholesterol, consistent with a potentially beneficial effect on
cardiovascular risk. Although most fasting is generally regarded
to reduce cardiovascular risk, over-zealous fasting for protracted
periods is not without risks of reducing myocardial mass alongside
reductions in other components of reduced lean body mass.
Conclusion
The use of intermittent fasting offers the potential to improve weight
loss and enhance the cardiovascular health of overweight and
obese individuals with type 2 diabetes and reduces cardiovascular
risk. Limiting calories in this way can reverse diabetes. This type
of intervention is cost-effective and associated with a low risk of
adverse events.
Declaration of conflicting interests
The authors declare no conflicts of interest in preparing this article.
Funding
This research received no specific grant from any funding agency in
the public, commercial, or not-for-profit sectors.
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