In a recent article (entitled ‘Is Eating Little And Often Still Relevant?’), I posed the question of whether eating little and often offered all of the benefits that have been suggested by the health and fitness industry, as well as introducing the idea of ‘intermittent fasting’.
To re-cap, intermittent fasting involves completely refraining from food and energy intake for a set period of time, or consuming a very low level of energy for a set period of time. Both of these protocols are then followed by a re-feed.
Two popular protocols:
- The 5:2 diet involves 5 days of normal eating where you just eat to satiety and 2 days where you restrict you energy intake to 25% of your usual daily intake. It is recommended that there is at least one day of normal eating in between the low energy days.
- The 16:8 diet involves 16 hours of complete fasting and an 8 hour window where you consume your daily food intake.
Could this be how our pre-historic ancestors would have lived? Although it would have been much less defined than 16:8 or 5:2, there would have been periods where they would have feasted (when food was available) and then periods where they would have to go without food and energy (when food was scarce). It is unlikely that would have free access to food. They survived and thrived, they would have been lean despite the fact that they allowed their bodies to go into so called ‘starvation mode’.
So you go without food for an extended period of time, our blood glucose levels fall and stored glycogen has been pretty much exhausted. Insulin levels are also very low. The amount of time this takes to occur does vary depending on previous activity level as well as the size and energy content of the last meal (there is also a certain amount of individual variance).
Your body is then forced to dip into our muscle and fat reserves to provide energy in response to the lack of available glucose. In a non-trained individual this state is characterised by low levels of insulin and glucose, it is realistically the only time when you will actually break down fat and use it as an energy source.
So what does this mean for the body?
If you can start to use body fat as a source of energy then this can help us to reduce levels of body fat you are carrying. You will also find that it is much easier to control the amount of energy you are ingesting, particularly if you follow the 16:8 protocol, which can help with weight management and/or loss. But is it just body composition and weight management that intermittent fasting can help with?
Various studies have shown that a number of health markers also appear to improve following a period where intermittent fasting is practiced. These being:
- Reduction in systolic blood pressure
- Reduction in LDL cholesterol
- Decrease in IGF-1
- Increase in insulin sensitivity (Which may be linked to the reduction in IGF-1)
The reduction of IGF-1 is particularly interesting as reduced levels of IGF-1 have been linked to a reduction in the ageing process in rodents as well as a reduced incidence of cancer and other life threatening conditions.
Once subjects in these studies returned to normal eating patterns these health markers did return to their original levels eventually. These findings are to be expected, but is intermittent fasting something that is sustainable in the long term?
If you look at both the 16:8 and 5:2 protocols they are easily sustainable for most people.
16:8 for example; finish your evening meal by 8pm in the evening and hit the hay by 11pm, wake up at 7am after 8 hours sleep. The first 5 hours of the day you will have to go without food or energy. Tea, coffee and water are allowed until 12 noon when you can eat your first meal of the day. Basically you are fitting your food consumption into an 8 hour window, followed by 16 hours of fasting, hence the name 16:8. How you choose to do this is entirely up to you. Practically it makes sense to have your period of fasting at night.
The 5:2 diet involves two days of caloric restriction which are separated by either two or three days of normal eating. The two days of caloric restriction involve consuming only 500 calories if you are female or 600 for males. It is tough, but your body adapts and if you work Monday to Friday you can always have one of your calorie-restricted days at the weekend so that you can keep energy expenditure to a minimum.
Not only does intermittent fasting have the potential to benefit your health it can also make your day a lot more productive. Stopping every 3-4 hours to eat can be a chore; it will break your rhythm during a working day, not to mention the disruption that it can potentially cause to your social life and leisure time, as you worry about how you will fit your meals around your activities. You will also find that you spend less time preparing food.
If you are looking for a new eating plan or are simply curious then why not give it a go?
(Image Source www.http://blog.lef.org/2013/07/want-to-live-long-try-intermittent.html)