There’s lots of interest in fasting for health these days so I am going to share what I’ve learnt.
What is intermittent fasting?
Intermittent fasting is when is an eating pattern where you cycle between eating and not eating.
There are no hard rules to how fasting should look but these are the commonly practised types of fasting:
- 16:8 or 16/8 fasting: A fasting cycle with an 8-hour eating window and 16-hour fasting window (i.e. no eating for 16 hours straight). Also known as time-restricted fasting.
- 5:2 fasting: A fasting cycle where you’d eat normally for 5 days of the week and with restricted energy intake for the other two days. Food intake is limited to 500-600 calories and it’s usually not over consecutive days i.e. 3 days of regular eating, 1 day of reduced caloric eating, 2 days of regular eating, 1 day of reduced caloric eating. Usually referred to as intermittent fasting.
- Wet fast: fluid intake is allowed.
- Dry fast: no fluid intake during fasting hours e.g. no fluids for 16 hours. Usually for religious reasons.
In a nutshell, fasting is about allocating time to eating vs. not eating.
How does fasting help you lose weight?
Most people are interested in fasting largely because of the weight loss or fat loss associated with it.
From a physiological perspective, it’s about what happens in your body during fed state vs. fasting state.
In a fed state, insulin levels is elevated. This is a hormone that’s involved with anabolic processes (building up, storage). Insulin leads to the removal of excess glucose from the bloodstream and the end product of the anabolic process is fat.
During fasting state, insulin levels are low and there is not enough glucose for energy. Fats are broken down into ketones by a process known as ketosis.
When you are fasting, there are two pathways in which the weight loss can occur:
1. Burning of fat via ketosis
2. Reduced calorie intake
3. Behaviour change: become more mindful of what you are eating so you may start to choose healthier foods
These are textbook mechanisms of what may happen with fasting. I highly recommend anyone who’s looking to lose weight to consult a dietitian for advice.
Like exercise for chronic pain, it’s easy to lookup back pain exercises or neck stiffness exercises on Instagram or YouTube. There are tons of them but most aches and pains don’t go away with Instagram rehab. The reason is because it’s a cookie cutter approach to pain management and it doesn’t take into consideration you as a unique individual, your lifestyle, and your goals.
So, I highly recommend speaking to a dietitian. Talk to them about what you are hoping to achieve with fasting and what sort of results you are expecting. They will 100% discuss your eating habits, food choices, as well as your lifestyle. Don’t forget to bring up any previous experiences you’ve had with weight loss. They will take all of these into consideration to formulate a plan that is more likely to work than a self-directed program.
Who should not try intermittent fasting?
Again, there’s no hard and fast rule on who can or cannot fast. However, in some cases, fasting should be attempted only with profession supervision.
If you are living with eating disorders or if you have a history of eating disorder, please do not attempt fasting without medical advice. The patterns of eating during fasting may trigger binge-restrict eating cycles. Likewise, anyone with poor relationships with food or eating should be extra cautious when considering fasting.
For diabetic patients, fasting is tricky because you’d have to take your body’s ability to regulate insulin into consideration. Your health care provider may suggest using continuous glucose metering to make sure your glucose levels are okay during fasting.
Individuals with gastric or acid reflux issues, fasting is possible but it’s highly recommend that you ease into it. You may want to start with a 12:12 cycle (12-hour eating window, 12-hour of no eating) then work your way to a 14:10, and finally going into a 16:8 cycle.
If you are trying to conceive, fasting may be unsuitable for you. It is not uncommon for women to miss their period with fasting. It could be a in-built evolutionary response where your body doesn’t want you to have a baby when food is a scarcity. That makes sense to me. If you really want to fast though, there were suggestions that trying a more relaxed fasting “format” like the 12:12 cycle may work.
Brad made a really good point that most athletes, especially high output/endurance athletes, struggle to eat enough calories with regular eating patterns. This is especially challenging if they are on a clean diet as well (no junk food, empty calories). So, athletes would really need to consider if could consume enough nutrients with time-restricted feeding and if their performance/recovery would be affected by it.
How to break fast?
Personally, I have never attempted to fast before so I found this interesting.
Apparently if you are coming out of a fast, you have to be careful how you eat or you might just end up gorging food. That does make sense to me.
So the recommendation that you snack a little at a time as you are coming out of a fast and work your way up to a meal later. Makes sense to me.
For those who struggle to fast, food may be seen as a reward function. So, probably better to be careful not to over-reward yourself.
It’s interesting how fasting look like in the modern day. What started as a religions practice/logistics issue (e.g. hunting/gathering life where you have to fast because there was no kill for the day) is now a gaining traction as a lifestyle option for good health.
I have yet to look into the research behind the recommendations mentioned in the AMA. If you would like discuss any of the issues relating to fasting, do research out directly to the speakers.
If you would like a referral to an evidence-based dietitian I can personally vouch for, drop me a message via the form below. I can put you in touch.