Fasting - good for your soul, good for your body?

Not eating or drinking for 25 hours may be good for your soul, but is it good for your body? And what about the idea of regular fasting?

On a very basic level, taking in less calories than you use each day will lead to weight loss, as you burn up your energy reserves, mainly in the form of fat. The minimum number of calories needed for basic body functions is known as your Basal Metabolic Rate (or metabolism as it is generally referred to). So, by not eating or drinking for a day, you could certainly lose a little weight (in addition to dehydrating), but realistically, you will probably overcompensate by eating a hearty meal before fasting, and then be so ravenous after that you will stuff yourself again. It’s even possible that you might put on weight, given that significant exercise during that time is unlikely. So, if a 25 hour fast isn’t going to help, what about shorter, but more regular fasts? This is known as ‘Intermittent Fasting’ (IF). At one end of the spectrum IF could be not eating for 24 hours once or twice a week, and at the other end is the more popular ‘5-2 Diet’, where one eats normally for 5 days, but reduces calorie intake to 5-600 for 2 non-consecutive days. Thankfully, unlike my 25 hour fast, IF lets you drink.

So, once again, on a very basic level, if you take in fewer calories than you burn, you will use your energy reserves and lose weight. But is there any evidence to show that intermittent fasting of this nature is actually helpful in real life?

A study in Nutrition Journal has shown that obese women can lose weight and reduce the risk of cardiovascular disease through combined IF and calorie restriction. But other studies, such as one in the American Journal of Clinical Nutrition found that women who do Intermittent Fasting can lower their glucose tolerance (a precursor to type-2 diabetes and an increased risk of cardiovascular disease) and potentially damaging your metabolism by altering hormonal systems. The same journal published another report that showed healthy, normal-weight women getting some benefit from only having one meal a day, but also suffered from significantly increased hunger (no surprise there), blood pressure, and cholesterol. So, it’s not clear cut, and results differ further between men and women. One thing we can be sure of is that IF could present some rather significant dangers.

Other things to keep in mind about IF:

It could trigger or exacerbate eating disorders, through excessive calorific restriction or bingeing.
Fasting can lead to increased cortisol levels, especially amongst women. This is the stress hormone, which helps the body release fat as energy in the very short term, but soon after starts to break down muscle mass instead (amongst other symptoms, including osteoporosis, impaired immune system, etc.)
You will end up thinking even more about food than normal, which is not a good way to get through your day.
You may rely too much on caffeine (since it is allowed in most IF plans) as a stimulant to get you through the hunger pangs. Eventually this will have a negative effect on your sleep, and also increases your cortisol levels (see above).
Unless you are very disciplined, it is likely that the meal you break your fast on isn’t going to be all that healthy. It will probably have excessive amounts of foods likely to spike your blood sugar levels, and potentially cause gastrointestinal issues, food intolerances, and even diabetes.

With that in mind, we at FreeRange Fitness really can’t recommend Intermittent Fasting as a healthy way to lose weight sustainably. It is important to remember that not only are there very rarely any safe short-cuts to weight loss, but you would be far better off developing good eating habits, combined with regular exercise.