Please note: For some people fasting works very well however for some people who have a binge eating disorder, skipping meals can stimulate your cravings beyond your control and hence for these people you may need to eat small regular healthy meals to keep your appetite down. Once you learn to manage the binge eating (professional help is recommended) then you can experiment beyond small regular meals.
Fasting is a topic that is gaining lots of interest, and is definitely growing in popularity. Indeed respected scientific bodies like the CSIRO are launching intermittent fasting diets for weight loss so it is becoming more mainstream.
To me the theory makes sense – humans evolved in harsh environments. There is no way we would have had 3 meals a day ready to go. We may have had 1, at best 2 meals a day. So humans evolved to not eat for periods. Not only did we evolve to survive fasting, it is possibly good for us.
Whilst it is way too early to be making clear recommendation or guidelines on this it is still very interesting stuff. There is indeed a large body of research to support the health benefits of fasting, though most of it has been conducted on animals, and only small amounts in humans. Still, the results have been promising. Some of the known benefits so far include weight loss, improving blood sugar and insulin sensitivity,improved risk factors of heart disease, reduce oxidative stress and inflammation and preservation of our learning and memory functioning.
There are many types of fasting so it really means you can find out what works for you and your situation. Fasting does not have to be having nothing, it could mean water only for a period, it could mean having a very small amount of food, or it could mean only eating in certain time periods. So there is quite a lot of flexibility, but let’s go through some of the common terms you might here.
- There is intermittent fasting or alternate fasting which is when we might fast for a day then eat normally the next day. One variation of this is called the 5:2 diet and has been popularised by Dr Michael Moseley, a British Dr and TV personality. It means you eat well but normally on 5 days of the week, and very little, less 500 calories for the other 2, so you net weekly amount is still less and you lose weight. This is quite an easy and reasonable place to start if you are thinking of trying out fasting.
- There is the fasting mimicking diet called the FMD where you vary your intake over 5 days. On day 1 you eat 50% or half as many calories and day 2 to 5 you eat a third of your usual calories.
- And finally there is time restricted fasting where you only eat in a certain number of hours in a day, perhaps a 4 hour window or 8 hour window.
For weight loss specifically there are a few things to consider
- The first is convenience = When you are fasting say 2 days a week, it means over the that whole week you are taking in less calories. So for some this is really convenient, it means you only have to think about prep food 5 days a week and 2 days eat very little, and it can be cheaper too.
- The second is how you respond to it – for some the hunger they will feel on those fasting days may drive them to binge eat and that is obviously not good. So it depends on how you respond to fasting
- The third is its effectiveness. For the CSIRO “Flexi” fasting program it showed participants in the 16 week trial lost an average of 11kg or 24 lbs and saw improvements in cholesterol, insulin, glucose and blood pressure. Some studies indicate that there is no difference between fasting or just overall reducing your calories, so again, you don’t have to do it like this and it is really just what works for you.
One thing I have seen is a few people fast really easily, but when they start to eat again they put on lots of weight. The theory behind this is that their body has flicked into a famine mode, meaning it will reserve energy when there is none coming in, but when you eat again it will store everything as fat in case there is another famine or fast in the future. In these patients I sometimes recommend the opposite of fasting – small and regular healthy meals to take the body out of the stress and famine mode, so it feels safe to lose the weight and stops storing it. But this is just my experience and I cannot say this is based on studies.
As always there are a few safety considerations. One is that you have to careful you still get enough vitamins and minerals for health and sometimes you might want to consider a multivitamin supplement and fibre supplement. When you are starting out, start slow and go gently, don’t do prolonged periods. Be careful as some people get a bit lightheaded when they first start, so be careful driving or operating heavy machinery. And if you have diabetes or any other medical conditions including mental health conditions you absolutely must see your doctor first. In fact I it is recommended to do this under the guidance of a qualified health professional.