You’ve probably heard of at least one type of “fasting” diet. Perhaps it was intermittent fasting, or it may have been the 5:2 Diet. It’s a buzzword at the moment and it seems like everyone is talking about it, but does fasting actually work? And how does it affect exercise performance?
What is fasting?
The idea of fasting (for health, weight loss, and even for religious and spiritual practice) has been around for centuries and scientific studies on the effects of fasting were being carried out in the 1940s. However, our current preoccupation with fasting doesn’t appear to be for religious or spiritual reasons. In fact, the reality is that most of us are intrigued by fasting as a fast-track route to weight loss.
The allure of fasting is obvious. By abstaining from food for short periods of time, we can (it would appear) enjoy a normal diet and even a few treats…and still lose weight! But is fasting safe, sustainable and sensible, or is it setting us up for an odd relationship with food, without teaching us anything about long-term healthier eating?
Popular methods of fasting you may have heard of include intermittent fasting, the 5:2 diet or the 16:8 fast. Of course, there is also that infamous Horizon episode, “Eat Fast and Live Longer” from 2012 with Michael Mosley, which propelled fasting into the mainstream.
Pros of fasting diets
Fans of fasting claim that reducing food intake for a period of time can lead to a number of health improvements. The fasting is done for a set amount of time, before returning to normal food intake and this cycle is repeated on a regular basis. The supposed benefits include:
- living longer
- reducing the risk of heart disease, stroke and some cancers
- lowering cholesterol levels
- lowering the hormone insulin-like growth factor (IGF-1)
- improved digestion
- higher energy levels
- improved blood sugar level control
- reduction of risk factors which can lead to type 2 diabetes
- mental clarity, focus and concentration
All of these things sound good but more human trials and studies need to be carried out before we can draw any real conclusions beyond anecdotal evidence. The published results from studies is minimal, so it would be foolish to start making brash statements without further research being done first.
Cons of fasting
The idea behind any fasting diet is that when you restrict your calories or food intake, you force the body to burn fat for energy as there is no food in your system. When you do eat, the body will simply use this for energy, rather than any stored fat, so in theory, you can burn more fat by fasting. There are potential risks involved though, particularly if you decide to embark on a fast without doing your research or getting the support of a nutrition professional before and during this process. You put yourself at risk of the following:
- missing out on important nutrients, vitamins, minerals and fibre.
- ending the week on below the optimum levels of healthy fats, protein or carbohydrates
- taking in the wrong amount of calories to maintain your fat loss or muscle gain goals
- not having enough energy and nutrients to perform and recover from workouts
- damaging your approach to eating as a couple or family
- ruining the social aspect of eating (such as meals out with friends etc.)
This list isn’t exhaustive and there are a number of different factors that could have a negative impact. Everyone is different and their bodies have varied responses when subjected to drastic changes, so you need to fully evaluate the risks before embarking on a fasting diet.
How does fasting affect your workouts?
Plenty of people do fasted cardio (doing cardiovascular workouts in the morning before eating) and it’s a popular approach for fat loss amongst bodybuilders and physique athletes. The question is whether it’s significantly worthwhile. The jury’s out, and there is no evidence to suggest any scientific basis to working out on an empty stomach; no studies have shown that fasted cardio will burn more fat or increase post-workout nutrient partitioning.
If getting your workout completed before you eat works for you, suits your schedule, or allows you to push harder without a full stomach, then there’s no harm. Some people report that this method makes them feel sharper and more focused but others are adversely affected and may feel faint and dizzy when following this method. The important thing is to make sure your nutrition is sound on a daily, weekly and more long-term basis.
How to fast safely
If your goal is muscle gain, size and mass, increased power or athletic performance, it seems sensible to eat regularly (and enough) to optimise digestion, protein and amino acid uptake and your recovery.
We highly recommend you consult a professional nutrition expert before you decide to fast, whether for weight loss or for fat loss. It will still be important for you to get the correct balance of macronutrients, and well as micronutrients, vitamins and minerals. You will need to pay even closer attention to the content of your meals than you would if you weren’t fasting and we would encourage you to also spend time working on a sustainable way of healthy eating that you can continue to do for the rest of your life after fasting.