Fasting

After being obsessed with eating as much as possible for my entire athletic career, I’m now having a change of heart. I’ve never tracked calories, but I’ve always eaten as much as possible. My reasoning has been that I should avoid low energy levels which could reduce my capacity to complete the next training session and that I should not risk losing muscle mass which could make me weaker and more injury prone in general.

But after critiquing the type and amount of fuel needed for exercise (see my post Fat as a Fuel), it’s clear that not all sessions need to be done with high carbohydrate levels and there are significant endurance and health benefits from training in a fasted state.

But, in this post, I wanted to shift the focus off training and onto health and longevity. Fasting, and especially prolonged fasts of up to a week or more, have been found to provide a wide array of health benefits.

Fasting for Health

Dr Valter Longo and Dr Satchin Panda are two leaders in this area that I’ve followed for some time now and the research they have been doing is extremely interesting. They have been independently examining the effects of nutrient timing in a wide range of organisms, from humans to microbes, and are finding that across the board, more is not always better. No surprises that obesity resulting from a positive energy balance is bad, but the real surprise is that balanced nutrition all of the time is not actually optimal for health. Balanced nutrition, cycled with periods of fasting, is better, EVEN when total calories are identical.

[ezcol_1half]

[/ezcol_1half] [ezcol_1half_end]

[/ezcol_1half_end]

It’s also noteworthy that adding periods of fasting in to an unhealthy diet delivers bigger improvements than adding them to an already healthy diet. The easy way to think about it is that there are more fixes that the body can achieve during the fast in someone that has more damage. The standout examples are radical reduction in cancer mass and rapid reversal of type 2 diabetes. There is benefit for all, but the main excitement from this research is around prevention and even treatment of metabolic diseases which are public enemy number one.

For the otherwise healthy person, the benefits include:

• Higher energy levels, improved energy stability throughout the day and improved mood due to improved metabolic flexibility (less dependence on constant carbohydrate consumption).
• Improved insulin sensitivity due to sustained decrease in blood glucose.
• Improved cell function due to autophagy (clearing and reusing dysfunctional organelles and misfolded proteins).
• Improved organ and immune function due clearance of old cells and stem cell-based rejuvenation of new cells.
• Reduction of inflammation due to an improved immune system.
• Visceral fat loss due to improved ability of cells to accept ketones which are made from fat.
• Gain in lean muscle mass (at least in males), counter intuitive to most.
• Increased cognitive performance due to the presence of the ketone β-hydroxybutyrate.
• Lengthened lifespan and healthspan due to the delay of chronic illness.
• Reduction in autoimmune conditions due to clearance of old autoimmune cells and creation of brand new cells which are not autoimmune.
• Reduction in general chronic joint pain, although the mechanism is not well understood.
• Increase death of cancerous and pre-cancerous cells due to their inability to generate energy sustainably on ketones.

The confidence in the research drops off after that and it has yet to be determined exactly how best to structure the cyclic fasting. Here are some common options being investigated by researchers.

• A whole day fast once per week.
• 5 days of a fast mimicking diet (very low calories) once every month.
• A 5-day water only fast once every 2 months.
• A 14-day fast once a year.

Many of these benefits are also observed in people on a ketogenic diet (high fat, low carb, low protein), but not to the same degree. One study found a better response over a 6 month period from just one five day period on a fast-mimicking diet embedded into a Mediterranean diet

than people on a ketogenic diet for the entire six months. (A fast-mimicking diet is a diet proposed by Dr Longo consisting of a very low calorie, plant-based diet taken for five days. During this period, metabolic changes occur that parallel those obtained by water-only fasting.) This is a tough comparison though, because a ketogenic diet should be tailored to the individual for maximum benefit, and benefits some people hugely but others very little. Basically, it’s hard to get right without taking measurements to figure out how stay in ketosis and still feel good. Fasting seems to work across the board and with less time on a highly restrictive diet

Extreme or Normal?

While this may sound extreme to the uninitiated, these ideas fit intuitively into evolutionary and physiological frameworks. Nothing in nature has constant access to nutrition due to daily, seasonal or random variation. It was always a struggle to find food in our evolutionary history, and organisms throughout the food chain spend large amounts of time without food. It is only in the last 100 years, or by some measures since the agricultural revolution (10,000 BC), that food availability has been so high. Modern society features one confused species living outside of it’s nutritional habitat.

Physiologically, it makes sense to think that our metabolism needs periods of stress, followed by adaptation to that stress. For example, consider how we treat our musculoskeletal system when training for a sport, with a mixture of hard sessions, easy sessions and recovery. The body adapts to stress by improving the function that was stressed. Growing cells, adding material, up-regulating enzymes, up-regulating genes may require a similar process. Our body is an adaptive machine. If you want your metabolism to be fit you have to train it.

The theme that jumps out is cyclic stress. This is not a chronic stress like working a high pressure job long term. When the body is stimulated with the stress of low nutrition, this elicits a change in cellular metabolic processes. But just like with training, it is the recovery that really matters. This is called the refeed. Old cells, organelles and waste are cleared, and stem cells are activated, in reintroduction of nutrition. This causes the most powerful regenerative event other than birth known to science.

Another way of looking at this, one held by Dr Longo, is that it is more useful to think about fasting as a biological “Plan A” alongside the biological “Plan B” of rapid growth. Whilst he acknowledges that what we call the body’s stress response is activated when we fast. He points out that fasting and eating are both totally normal phases to be in and common throughout the natural world, from bacteria to flies, mice and humans. It is largely only humans following the modern western lifestyle, with almost no awake time in the not eating phase, that break the mould. Cells in a low nutrient environment adopt Plan A: they do the house cleaning, recycle as many old parts as possible, increase efficiency and increase resilience. Cells in a high nutrient environment adopt Plan B: they reproduce, grow, and divide quickly at the expense of repairing damage that begins to accumulate. Cells that move through high nutrient availability and low nutrient availability then become stronger and more efficient. More specifically, there are less misfolded proteins, less dysfunctional mitochondria and less inflammation.

Risks

So what can go wrong? The most concerning complications relate to medication and an individual’s medical conditions. Fasting demands a lot from many biological functions and if some of these are offline because of medication or individual make up, then it is possible to become sick very quickly. So always check with your doctor if this could be you.

Although a temporary reduction in lean body mass can occur, after the refeed there will be a return to normal. Remember that a healthy amount of resistance should be the primary driver for muscle mass increase and a week-long blip on the radar is negligible in the long run.

Low energy levels during the fast are expected as your body establishes a new metabolic set point. This might makes multi day fasts prohibitive for someone with an active job so finding a fasting type that fits considers lifestyle is essential for long term compliance.

It is important that long term energy expenditure is taken into account and that long term calorie restriction is not mistaken for cyclic fasting. Consuming less calories than your body needs long term is not the objective because it lacks the highly beneficial refeed. Once the body goes too long without nutrients, muscle tissue begins to be broken down as a source of nutrients, and at this point the body enters starvation. Starvation is a slippery slope and people doing extremely long fasts require constant medical attention.

A further consideration is that females may respond differently. Many of the studies in this area observe males, and research on females, who have important differences in metabolic regulation compared to males, is harder to come by. This is an area that needs to be explored further.