Fasting - fad or fab?

Is fasting just a fad? What if you don't need to lose weight? We look at insulin resistance and break down the jargon - 5:2, fast 800 and TRE!

Fasting is not new, it has been commonly done as a form of purification in a religious setting but recent studies are shedding light on how it actually works.

When you fast, your body saves energy by recycling old or damaged cells and switches to burning fat. When you break your fast, your body responds like the desert after rain. It starts creating new white blood cells and may help reset the immune system.

When the brain is using fat as fuel instead of glucose, it also secretes BDNF (brain-derived neurotrophic factor), which is thought to prevent dementia by strengthening neural connections and increasing the production of new neurons.

Regular fasting helps to improve insulin resistance and lowers blood sugar. Insulin resistance is when your muscles and liver become less sensitive to the release of insulin (see above). When this happens, your pancreas is working harder, you start storing fat around your organs instead of the usual places and yet you still feel hungry all the time.

Dr Michael Mosley says: "It's as if you're constantly pouring money into your bank account, and then finding it incredibly hard to get it out again. High levels of insulin prevent your body from accessing and burning its energy supply."

I've been a fan of Dr Mosley's books and TV shows as the advice seems sensible and backed up by research (both proper trials and testing on himself!) He has popularised several diets based on fasting:

•  Originally the 5:2, which is 5 days of normal eating and 2 days of fasting (500 - 600 calories per day). 
• The blood sugar diet, which is 8 weeks of reduced calorie intake (800 calories a day).
• The fast 800, which is a combination of the blood sugar diet to kick-start weight loss then followed by a modified 5:2 but having 800 calories instead of 500 on the 2 fast days. It also includes time-restricted eating (TRE). I used to think that rapid weight loss was bad for you but it is actually okay as long as you get adequate protein (don't just drink cabbage soup). It also lets you taste success early and gives you motivation to keep going, as well as more energy to then start exercising.
• Time-restricted eating is where you only eat during a 8 to 12 hour window during the day, eg 9am to 9pm, or 8am to 4pm. By itself, it is not enough to lose weight but it gives your digestive system a chance to rest and clear out the old cells and debris. 

If that was confusing, here's the take-home message...
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 If you are at a healthy weight, some fasting may still benefit you. The easiest way to do it is by time-restricted eating, for example, have an early dinner and not snack after that.

 If you are looking to eat more healthily, low-carb with adequate protein and fat is the most sustainable and tastiest way to go.

 If you are healthy but want to lose some weight, have clear goals and restock your fridge and pantry with alternatives that you can eat safely. You can experiment with the 5:2, fast 800 or any other combination along with increasing your exercise.

 Fast-paced exercise e.g. 3 bursts of 10 minute brisk walking versus 10000 steps a day is easier to do and to stick with long term.

 Getting enough sleep is also key to having fewer food cravings in the day.

 If you have a health condition or are pre-diabetic, please seek medical advice or inform your health professional before starting on any diet.