The benefits of Intermittent Fasting
Can when you eat be more important than what you eat?
Is intermittent fasting (IF) the key to weight loss?
Are you thinking about changing your eating strategy to optimise your health?
What does the evidence say? Let’s dive in.
Before I get into it there’s something you should know.
There is no perfect diet.
Intermittent fasting is not actually a diet.
Your diet is what you eat.
Also fasting may or may not be suitable for you. Anyone under 18, the elderly, pregnant women, people with chronic illnesses, eating disorders and anyone unwell should avoid fasting.
Ok so what is fasting?
It’s the voluntarily abstaining from some or all food and drink for a specific period of time, usually for religious, spiritual, health, or personal reasons.
Fasting has been practiced for thousands of years and has been associated with numerous health benefits.
Interestingly, it has also been used as a healing method for diseases in the past.
There are actually lots of different types of eating strategies to prevent obesity or weight gain.
They can be broadly broken down into 3 types.
- Calorie restriction.
- Intermittent fasting or IF.
- And time restricted eating or TRE.
In this article when I use the term fasting by itself, I’m referring to both intermittent fasting and time-restricted eating.
Intermittent fasting involves alternating periods of fasting and eating.
This can be done in various ways, but the most of the most popular forms is the 5-2 diet.
This essentially means eating completely normally for 5 days and then restricting calories for 2 days of the week. There’s usually a 60–100% energy restriction on fasted days.
An increasingly popular form of fasting is TRE (my preferred method).
Time-restricted eating involves eating all your daily calories during a specific window of time each day and fasting for the remaining hours.
The most common approach is to only eat within an 8-10 hour window each day, such as eating from midday to 8pm and fasting for the other 16 hours.
The idea behind TRE is that by limiting the time of day during which you eat, you can improve your body's metabolism and other health markers.
What is the science behind it?
One of the primary physiological effects of fasting is a shift in energy metabolism from glucose to fatty acids and ketones.
It’s a concept known as metabolic switching.
Let me break it down.
Glucose is the primary energy source for most tissues during the day and in the fed state, insulin is the main hormone that is involved in helping your body use this glucose for energy.
However in the fasted state, glucagon is the primary hormone, and glucagon triggers the liver to break down it’s glycogen into glucose for energy.
After you eat a meal, glucose is utilised for energy and fat is stored as triglycerides in adipose tissue.
During prolonged periods of fasting, insulin levels decrease, the body's glycogen stores are depleted, while glucagon and other hormones involved in lipid metabolism increase.
At this point your body must turn to fat stores for energy.
Triglycerides are the main fat found in adipose tissue are converted to fatty acids and glycerol, which are subsequently metabolised for energy.
The liver then converts fatty acids to ketone bodies.
And during fasting, ketones become a major source of energy for many tissues, especially the brain.
The onset of the metabolic switch is the point where liver glycogen stores are depleted and fatty acids are metabolised.
This tends to happen 12hrs after the cessation of food intake.
Ok so how does fasting help?
Here are the 3 key benefits:
1: Weight loss
Both methods can reduce overall calorie intake by limiting the time window during which food is consumed.
A study published in the International Journal of Obesity compared the effects of TRE and IF on weight loss in 116 overweight and obese adults.
The participants were randomly assigned to either TRE (consumed all calories within a 6-hour period) or IMF (where they consumed 25% of energy needs on two non-consecutive days each week).
After 12 weeks, both groups had lost weight, but there were no significant differences in weight loss between the groups.
By shortening the eating window, you’re able to reduce the total amount of food consumed, leading to a reduction in overall calorie intake.
This calorie restriction can then lead to weight loss over time, as the body begins to use stored fat for energy.
On top of this, we’ve talked about the concept of metabolic switching where the body switches from using glucose as its primary fuel source to using stored fat for energy.
This shift in metabolism can lead to increased fat burning and weight loss over time.
A review paper which looked at 27 intermittent fasting trials found a range of weight loss from 0.8% to 13% of baseline weight with no adverse effects.
2. Improved metabolic health
Intermittent fasting and time-restricted eating can improve metabolic health markers, such as insulin resistance and blood sugar levels.
I actually spoke about insulin resistance in a previous video if you want to check that out.
A review of 12 studies found that IF improved insulin sensitivity and reduced insulin levels.
Another study of TRE in overweight adults found that it improved insulin sensitivity and decreased blood pressure
3. Reducing inflammation
Both intermittent fasting and time-restricted eating have been shown to reduce inflammation in the body.
A recent paper from Satchin Panda’s team published in Cell metabolism determined that TRE decreases genes involved in inflammatory signalling in mice.
Another review of 13 studies found that intermittent fasting reduced markers of inflammation, such as C-reactive protein and tumor necrosis factor-alpha.
A study of time-restricted feeding in healthy adults found that it reduced markers of inflammation and oxidative stress.
It’s also worth mentioning that fasting increases autophagy.
This process is essential for maintaining cellular homeostasis and preventing the accumulation of toxic substances within cells.
Autophagy has been shown to play a key role in reducing inflammation, as it helps to remove damaged cells and cellular debris that can contribute to chronic inflammation.
Studies have shown that IF and TRF can promote autophagy, leading to a reduction in inflammation and improved overall health.
Ok so which method is better for losing weight?
Both strategies have been shown to be effective for weight loss, and the choice between the two may depend on individual preferences and lifestyles.
A recent meta-analysis of 19 papers concluded that TRE may be an effective strategy for improving metabolic health and preventing metabolic diseases.
However the majority of the studies included in the paper were limited by small sample sizes and short study durations.
Right so are fasting diets (IF and TRE) better than good old calorie restriction for weight loss?
It seems pretty inconclusive.
A study in 2019 looked at all 3 methods of weight loss and a determined that there were no differences in weight or body fat loss in 9 out of 11 studies.
The choice between IF and TRE may depend on individual preferences and lifestyles.
Overall, the evidence suggests that both fasting strategies and calorie restriction diets can be effective for weight loss.
Also if you want to learn more about intermittent fasting and time-restricted eating then watch this video.
Dr Panda is one of the worlds leading experts in circadian science.
A good watch.
A quote from a great
Stay healthy,
Z
Connect with me on socials
https://www.youtube.com/@DoctorZobir
https://twitter.com/DoctorZobir/