Why would you want to go without food and have to deal with gnawing hunger? Fasting helps you get lean while staying muscular. It also triggers the body to heal and optimise itself. Hollywood stars like Hugh Jackman and Terry Crews (both in their late 40s!) have used intermittent fasting it to look good and feel great!
Physiologically, fasting triggers internal clean-up processes to combat disease, fine-tune hormone levels and helps give your digestive system a much needed break. Psychologically we come to see how we eat when we're bored or stressed, how food forms a social bond and the impact of advertising on how we eat. Fasting has been a part of many religions and spiritual traditions, including Christianity, for millennia.
The body enters the fasting state roughly twelve hours after you last ate, assuming an average sized meal. The fasting state isn't an on or off state, and the effects become more pronounced the longer the fast. So why fast?
With no incoming energy from food, the body up-regulates it's fat burning machinery. This is why our bodies store excess energy as fat in the first place, and even the leanest individuals have weeks' worth of energy stored in fat cells. Hormones are produced to release fatty acids from adipose tissue such as human growth hormone (HGH), cortisol and hormone sensitive lipase (HSL). Fasting also triggers the body to increase the number of mitochondria in cells to burn more fatty acids as fuel. This fat burning state is called ketosis, and it can also be triggered by a low carbohydrate diet. However it can take the body a little time to adjust to burning fat as fuel, especially if it's been used to burning large quantities of carbohydrates. The deeper the level of ketosis, the less hungry you will become – the hunger pains do go away, and they get less over time. It's easy to see how fasting can be used for fat loss.
Fasting increases release of human growth hormone (HGH) which builds muscle (and burns fat). One study showed a 2,000% increase (yes, you read that correctly!) in a 24 hour fast.
Fasting also increases testosterone – a study showed a 180% increase in men at the end of a 56 hour fast! So yes, fasting can help you build lean muscle with minimal fat gain. Don't believe me? Check out Martin Berkhan and Brad Pilion – both lean and muscular guys that implement intermittent fasting.
A common fear with fasting is that you will lose muscle mass during the fast, however the body won't start breaking down muscle tissue for at least 72 hours. It knows it needs to preserve muscle tissue (as long as it's being used), and that it has plenty of adipose tissue to pull energy from, even in very lean individuals. The state of ketosis also helps to preserve muscle, as does the process of autophagy (below).
The body also needs amino acids to build new cells and function optimally, so it kicks off a process called autophagy. Autophagy is the orderly degradation and recycling of cellular components. The cells that are targeted by this process are those that are damaged in some way such as aging or cancerous cells. We all have cancerous cells in the body, and this process can help protect against a proliferation of those cells which is when problems from cancer arise.
When we eat, the body releases insulin to shuttle the energy and nutrients into cells. The more carbohydrates, and to a lesser extent the more protein, in the foods we eat, the more insulin is required. Frequently eating a lot of simple carbohydrates then makes the body less sensitive to insulin over time. The body then needs to produce more and more insulin to compensate, which makes the body even less sensitive to it leading to insulin resistance and finally type 2 diabetes. During a fast, the body does not release insulin as there is no incoming food and so it re-sensitises the body to the effects of insulin.
Fasting re-sensitises the body to hormones that signal hunger – leptin and ghrelin. These are often imbalanced due to overeating, both in meal frequency and food quantity, which causes us to eat more food than we require.
Fasting also improves your cholesterol profile – lowering small particle LDL (the bad cholesterol) levels by about 20% over a few weeks of intermittent/short-term fasting, while leaving HDL (good cholesterol) levels in-tact.
If we're eating all the time, our digestive system never gets a chance to rest. You know how you feel when you're constantly busy and never get a chance to rest? That's how our digestive system feels too. Fasting can help heal digestive issues such as bloating, constipation, colitis, leaky gut and candida.
Fasting, and ketosis, releases β-hydroxybutyrate (BHB) as an energy source, but BHB also inhibits inflammatory proteins. Left unchecked, these inflammatory proteins lead to disorders including autoimmune diseases, type 2 diabetes, Alzheimer's disease, atherosclerosis, and auto-inflammatory disorders.
Along with the anti-inflammatory effects above, fasting triggers your body to produce white blood cells that help fight off infection. The body can also produces stem cells that regenerate the immune system. Fasting for 72 hours has also been shown to be effective protection against the toxic impact of chemotherapy.
All of the above effects of fasting will help you live longer. Fasting also seems to increase the anti-oxidant capacity of the body, which further slows the effects of aging.
Fasting forces you to deal with hunger. You learn that it's just a biological signal saying your stomach is empty, that it will go away and it doesn't have to control your behaviour. Once your body adapts, you actually feel pretty good when fasting. You have more energy when ketosis ramps up, and you get more done without eating all the time. You learn to feel when you really need to eat, versus when you're just hungry. Now you know what it feels like to be hungry, be grateful for the abundance of amazing food we do have, and mindful of how many people go without.
When you do eat after fasting, that food will taste incredible! You'll also be more in tune with what your body actually wants to eat rather than just eating crap. You may develop a keen sense of smell for food in particular (I know I have!).
One of life's great joys is sharing a meal with loved ones. Celebrating holidays or just a family eating dinner together forms a strong social bond. Just keep in mind there can be a lot of pressure from well meaning loved ones trying to get you to overeat, or eat foods that aren't going to get you to your goals. If you're meeting people during your fasting period, make it an activity that doesn't involve food such as going for coffee, going for a walk or playing a game of football.
It's not surprising that food companies recommend we eat 3 meals a day plus snacks – they have a vested interest in us buying more and more food. I've heard many people say “oh I'm just eating because it's lunch time, I'm not actually hungry”. Listen to your body for hunger cues rather than looking at the clock. Also well-meaning food advisory groups tell us that we need to eat 3 square meals a day, but then why do we have the machinery to go without food for so long, and why does it promote such amazing health benefits?
This is a tricky one. We all have our comfort foods – things that we ate as kids that made us feel comfortable, safe and loved. Often when we're stressed or upset, we'll crave these foods. This is ok, as long as you're aware of it, but it becomes a problem when it's happening all the time.
Boredom also can be a trigger to eat, just to break up the monotony of sitting at home or in the office. Ask yourself are you really hungry? If not, try going for a walk instead or go read a book in the park.
There is a reason that fasting is used in religious and spiritual traditions beyond the physical and mental benefits outlines above. Fasting helps make us feel ‘lighter' – not so grounded and heavy, more able to feel energy and access higher states of consciousness. It's hard to really put this part into words - you'll just have to experiment for yourself.
It's not recommended to fast for more than a few days without medical advice. Also don't decide to jump head first into a three day fast if you've never fasted before – your body isn't used to it and you will struggle, especially if you're used to eating a lot of carbohydrates for energy. Try just delaying breakfast or skipping dinner, utilising a 12 to 16 hour intermittent fast a couple of times a week, and go from there. You can then try a 24 hour fast or longer, or even more frequent short daily fasts. Men respond very well to fasting, but it can be a little more hit and miss with women due to differences in our biology – experiment and see how you feel.
Don't do any strenuous exercise as your body adapts to fasting. Light exercise is ok, but otherwise let your body adapt first before training in a fasted state (which has it's own amazing benefits!) as the stress on the body can be a little overwhelming.