Intermittent Fasting: Benefits and Risks Explained

In case you are new to this term, intermittent fasting, also called Time-Restrictive Easting, simply means that you only eat within certain contiguous hours of the day. There are different protocols, like 12:12 (for example, eat 8 am-8pm, fast 8pm-8am of next day), 10:14 (10 hours eat, 14 hours fast) or 8:16 (8 hours eat, 12 hours fast).

In this article, I share my point of view about intermittent fasting. To understand why it might work, even if what we see (like fat loss) is in fact a side effect, we would need to explain what mechanisms are triggered in a fasting body. In short, intermittent fasting triggers the starvation state, since no easily accessible fuel (carbs and glucose) are being supplied. As a result, the body, which ultimate mission is to keep us alive by protecting our brain and our muscles, declares an emergency state and switches to an alternative, less efficient type of fuel: fat and ketones.

Intermittent fasting and insulin resistance

Studies prove that intermittent fasting improves insulin regulation. If we don’t eat carbs or protein for a long period of time, glucose levels won’t increase in our blood and we won’t need to secrete insulin to return to homeostasis (baseline glucose values). Therefore, intermittent fasting can work well for people with insulin resistance and even type 2 diabetes, always under medical supervision.

When there’s insulin resistance, especially if excess of fat tissue (adiposity) is present as well, many times the satiety-hunger mechanism does not work well. Satiety signals are not triggered or not correctly interpreted, and we keep eating beyond our physiologically satiety point, leading to more fat storage and perpetuating insulin resistance.

If the body is able to revert insulin resistance, via intermittent fasting or other ways, this satiety mechanism can be fixed and as a side effect, fat loss may be experienced.

Intermittent fasting and anti-aging

Studies show that intermittent fasting can slow down aging through multiple mechanisms.

Autophagia is an interesting one. Autophagia can be understood as the recycling of senescent and old cells and cell components. Our bodies clean up and reuse all this, in order to prevent garbage accumulation and promote optimal function. Autophagia is a natural process, but it slows down with age. Intermittent fasting has shown to boost it up, which makes sense since we are not giving new stuff (food) to the body, so it has to recycle as much as it can to keep functioning. A simple 12:12 protocol is thought to suffice to boost autophagia.

There are promising studies that show that autophagia can also work for cancer cells, thus intermittent fasting and autophagia could help reduce the risk of getting cancer and enhance the outcomes when used along cancer treatments like chemotherapy.

A simple 12:12 protocol is thought to suffice to boost autophagia.

Lastly, other studies also show that intermittent fasting helps maintain the length of the gene telomeres. The length shortens with cell aging, therefore longer telomeres mean less aging.  Longer fasts are needed for this though.

So yes, intermittent fasting seems to keep our cells younger.

Intermittent fasting and fat loss

Most people I know use intermittent fasting to lose fat weight.

In my opinion, the reason why healthy people lose fat with intermittent fasting is because they eat less. Period. There’s only that much that you can eat in 8 hours for example, if you are doing the 8:16 schedule. The downside is that this can lead to malnourishment and nutrition deficiencies as I will explain later, especially if held for long periods of time.

Exercise can be used in conjunction with intermittent fasting to boost fat loss. Try to schedule your workout at the end of your fasting window, so you can tap into fat as fuel sooner, and then refuel right away, that is when the body is more receptive to the repairing nutrients like carbs and protein. Unless you are used to training fasting, this would probably need to be a low to moderate intensity cardio workout (the famous zone 2), either on its own like a brisk walk, or in a metabolic circuit training using light to moderate weights and high repetition count.

Intermittent fasting and digestion/GI health

The GI system of the body is one of the few systems, besides the muscular system, that might benefit from rest, especially for those who tend to have GI issues like bloating and slow digestions.

Giving your stomach a break from digestion, and your gut time to complete the digestion and absorption of the food, is usually a good idea and common practice in traditional practices like ayurveda. Let things out before adding more stuff, if you know what I mean… It’s like starting the day on a blank canvas, the GI is clean and rested and ready to take on the upcoming day.

A 12:12 or 14:10 intermittent fasting should be enough to achieve this. Fasting for longer periods can backfire, leading to stomach issues and constipation.

Considerations about protein intake and intermittent fasting

For optimal use, protein should be provided in multiple smaller doses throughout the day, and not in one big intake. Therefore, intermittent fasting can hinder protein utilization.

This is particularly true for those trying to increase muscle mass (and training and eating for it) and for people on a plant-based diet, who typically need more volume of food to meet protein intake recommendations.

Intermittent fasting and cardiovascular health

This one may surprise you. Per the American Heart Association, a study of over 20,000 adults found that those who followed an 8-hour time-restricted eating schedule had significantly higher risk of death from cardiovascular disease – as high as 91%. People with heart disease or cancer also had an increased risk of cardiovascular death. Compared with a standard schedule of eating across 12-16 hours per day, limiting food intake to less than 8 hours per day was not associated with living longer.

We’d better stick to 12:12 to reap some intermittent fasting benefits, and avoid the red zone.

Intermittent fasting and dental health

This is something my dentist taught me recently: every time we eat, the acidity in our mouth increases, which can promote teeth erosion. Longer periods without food or drink other than water can then help keep our mouth healthier. Notice that some drinks like black coffee that are allowed during fast periods do increase mouth acidity.

Who should not do intermittent fasting

Any person with a health condition like iron deficiency, cardiovascular disease, osteoporosis, insulin resistance, etc. should always check with their physician before doing intermittent fasting.

In this same line, people struggling or recently recovered from an eating disorder like anorexia or bulimia, or disordered eating like orthorexia, may be at increased risk of relapses with a restrictive eating pattern like intermittent fasting.

And how about healthy people?

People who eat a plant-based diet, especially vegans, typically need larger amounts of food to meet the daily nutritional needs. If you are limiting the number of meals you eat to fit into a short timeframe, you can be at risk of nutrition deficiencies. I do not recommend aggressive intermittent fasting to those who follow a plant-based diet for this reason. 12:12 or 14:10 might be fine, but I encourage not to skip meals, just adjust the timing – for example, an earlier dinner and a later breakfast.

People who follow a plant-based diet are usually leaner, thus they may not benefit from the 8:16 protocol anyway.

Intermittent fasting, in summary

The gotchas:

• It can be challenging to get all daily nutrients, especially for those following a plant-based diet/vegan, which increases the risk of deficiencies.
• Protein utilization may be suboptimal.
• Increased cardiovascular risk if eating food is 8 hours per day or less.
• Can trigger eating disorders or disordered eating in susceptible people.

And the better:

• It can improve insulin resistance.
• It can promote fat loss if you are skipping meals or limiting your calorie intake, particularly if you time your workouts right at the end of the fasting window.
• It can help slow down aging.
• It can help with digestive and GI issues.
• It can help with oral health.

My recommendation

First and foremost, think about your why and what outcomes you’d like to achieve that intermittent fasting can support.

Second, think the timing that’s easier for you. For example, would you rather eat an early dinner, or a late breakfast works better for you? Or perhaps you prefer to skip lunch so you can leave earlier from work?

Third, consider these tips:

• implement it in a schedule of 12:12 (12 hours eating, 12 hours fasting) up to 10:14 maximum, to minimize malnourishment and cardiovascular risk.
• don’t go into 8:16 due to the higher risk of malnourishment and cardiovascular problems.
• if you cut down some food and calories, track your intake to make sure you are meeting the recommended daily nutrient requirements.
• it may be advisable to take a multi-vitamin or supplements if recommendations are not being met, but only temporarily, as food should be our main source of nutrients. Supplements can be vitamins, minerals, or things like protein powders for sensitive population.