Intermittent
fasting has been the subject of a lot of research and intense conversation of
late. A recent review article in The New England Journal of Medicine adds
fuel to the debate. What are the pro’s and con’s of intermittent fasting? Is it
the easiest way to lose weight? Is it the best strategy for health and
longevity? I don’t know if we totally have the answers to these questions just yet,
but some conclusions can be drawn from the data we have so far.
The Article
The article was
published in late December in The New England Journal of Medicine by two
researchers from John’s Hopkins University School of Medicine (Reference 1). The
main thrust of the article is to present the health benefits of intermittent
fasting. The authors argue that fasting turns on adaptive cellular responses that
improve glucose regulation, increases stress resistance and suppresses inflammation.
The article discusses
the three most studied fasting protocols:
-Alternate day
fasting.
-5:2 intermittent
fasting, where you fast for 2 days each week.
-Daily time
restricted feeding.
The article goes
on to describe research that found benefits of intermittent fasting on aging
and a wide variety of disease processes, including: cognitive function,
obesity, diabetes, cardiovascular disease and cancer.
Conclusions And Recommendations
1) This article
presents some very interesting research concerning the health effects of
intermittent fasting. This is a well written and well researched article
published in the top medical journal in the world. The researchers make some
compelling arguments about how fasting can improve health. I think the research
in this area is in a really early stage and we need to do a lot more before we
have any definitive answers.
2) Having said
that, most of the research has been on animals. This can be a problem because
animals have a very different physiology compared to humans and many times animal
research does not translate to humans much at all. The authors mention this in
the conclusion: “Animal models show that intermittent fasting improves health
throughout the life span, whereas clinical studies have mainly involved
relatively short-term interventions, over a period of months. It remains to be
determined whether people can maintain intermittent fasting for years and
potentially accrue the benefits seen in animal models” (Reference 1).
3) When it comes
to weight loss strategies, I am not at all convinced that intermittent fasting is
the way to go. I feel this way for several reasons:
-In most of the
studies that I have seen, there is no greater weight loss when comparing
fasting and a more standard continuous calories restriction. I researched two
of the weight loss studies cited in this review (References 2 and 3). These
studies compared continuous calorie restriction to intermittent fasting. In
both of these investigations, the amount of weight loss was the same whether
fasting was used or continuous calorie restriction was used as a method of
weight loss.
-While there were
some benefits to those who fasted, including improved fasting insulin and
insulin resistance, there were some negatives as well. Several other research investigations
that I have covered in my blog showed negative outcomes with diets using intermittent
fasting. These include: an increased LDL cholesterol, glucose dysregulation, increased
inflammation, increased hunger, a decreased physical activity level and a decreased
energy expenditure. If you want to reference these studies, please refer to
this older blog post (click here).
-There can be some
real side effects to intermittent fasting. This was apparent in both of the weight
loss studies that I downloaded from the review. In the British Journal of
Nutrition article, subjects in the intermittent fasting group were more
likely to report constipation, headache, feeling light-headed and being preoccupied
with food as side effects (Reference 2). Furthermore, the subjects fasting were
more likely to have deficiencies in important nutrients such as magnesium, zinc,
selenium and fiber.
In the International
Journal of Obesity article, subjects fasting were more likely to report
negative side effects such as lack of energy, headache, constipation, lack of
concentration and hunger (Reference 3).
-Another major issue
for me is the nutritional composition of the diet. If you are seriously
restricting your food intake several days each week, there is no way that you
will be getting enough vitamins, minerals, fiber, antioxidants, fruits, vegetables,
etc. Supplementing with vitamins is just not the same.
In conclusion, this
article on fasting in The New England Journal of Medicine is very
interesting. There appears to be some real
health benefits for animals. It remains to be seen if these benefits translate
to humans over the long term. As a weight loss strategy, it is my opinion that
fasting is not the easiest or most effective strategy.
References
1) de Cabo R, et
al. Effects of intermittent fasting on health, aging and disease. New
England Journal of Medicine 2019; 381:2541-51.
2) Harvie M, et
al. The effect of intermittent energy and carbohydrate restriction v daily
energy restriction on weight loss and metabolic disease risk markers in
overweight women. British Journal of Nutrition 2013; 110:1534-47.
3) Harvie M, et
al. The effects of intermittent or continuous energy restriction on weight loss
and metabolic disease risk markers: a randomized trial in young overweight
women. International Journal of Obesity 2011; 35:714-27.
