Is Fasting Healthy & What Are The Effects On The Body?

Fasting is mostly associated with religion, but for anyone considering a fast for the sake of weight loss in place of exercise, here’s some food for thought.

Whether you want to or not, we all fast every night when we go to sleep. This is a solid block of time – an average of eight hours – when we fast. For people keen to try fasting, this might come as encouragement; if you can go eight hours without food, then surely it isn’t too hard – just don’t think about food, right?

Not entirely. Will power aside, there are many medical professionals who recommend against fasting – especially for people with eating disorders, people who are highly active, elderly people and pregnant women.

Are there any benefits to fasting?

When you run on empty without food for more than eight hours or so, your body enters ‘ketosis’. Ketosis occurs when the body runs out of carbohydrates to burn for energy, so it burns fat. When your storage of glucose has been depleted, your body will begin to burn fat as a source of energy, which can result in weight loss.

The issue here is general misconceptions as to how weight loss works. Yes, if you fast it can potentially make you lighter, but it is not the same kind of weight loss that could be achieved by regular cardio and regular nutrition. The majority of medical experts will agree that when it comes to weight loss, fasting is not a healthy option.

intermittent fasting

Fasting and weight-loss

The weight loss from fasting is not substantial and can slow down your metabolism, meaning that with a slow metabolism the same meal you ate before you started to fast will be more fattening. It’s for this same reason that people on elastic diets, eating a lot and then nothing at all for certain amounts of time, skipping meals and neglecting protein and carbs amidst a busy day, will find their food more fattening when they eat. A good, fast metabolism is the result of consistent, healthy eating, among other things.

One other thing to bear in mind with regards to the supposed quick weight loss of fasting is that it will be gained back just as quickly when you start to eat normally again. The NHS states that there are numerous health risks associated with intermittent fasting.

People who fast tend to experience dehydration, largely because their body is not getting any fluid from food. As such, it is recommended that during Ramadan, Muslims consume plenty of water prior to fasting periods. Other individuals following fasting diets should ensure they are properly hydrated during fasting periods. Fasting can also cause heartburn; lack of food leads to a reduction in stomach acid, which digests food and destroys bacteria.

Fasting side effects

Dehydration, hunger or lack of sleep during a fasting period can also lead to headaches.

If your interest in fasting or skipping meals is weight loss, think again. Even if the side effects and discomfort of going without food appeals in light of losing weight, remember that initially, it will be water weight that you use – which you will then put on as quickly when you eat and drink again. Because of the lack of nutrition – going without important protein, carbohydrates, fats and vitamins will leave you unable to effectively exercise – and muscle gains are out of the question.

Though the pros and cons list is already looking pretty imbalanced, it’s worth noting that days of discomfort spent fasting for the sake of weight loss has an alternative; by running for 30 minutes a day on an incline you will be able to eat and also burn more calories, resulting in fat loss but also toning and muscle development. And by choosing exercise over fasting your metabolism will also be improved, meaning that you digest and process the food you consume so that it’s put to use rather than carried in excess.

Weightlifters and bodybuilders concerned over the realisation that sleeping each night is essentially fasting, worry not. Many pros suggest drinking a casein-whey shake before bed. Casein protein is broken down over several hours, meaning it is a good pre-emptive solution to any long periods of time without food if you’re fearing for your gains.

Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.

Faye Reid

Faye Reid

Writer and expert

Faye Reid has a Bachelor of Science in Sport and Exercise Physiology and a Master of Science in Exercise Physiology and Sports Nutrition. Faye has worked with numerous high-profile organisations, such as Men's Health, Sky Sports, Huddersfield Giants, Warrington Wolves, British Dressage and GB Rowing, providing her expert sports science support. Find out more about Faye's experience here: She puts her passion into practice as goal attack for her netball team, and in competitive event riding.

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