Problems Of Intermittent Fasting
For Young People

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Intermittent Fasting is an eating pattern that is currently being investigated as a realistic way for humans to eat to achieve the health benefits and life extension potential of calorie restriction without the misery.

So far results of human studies investigating IF have been pretty positive – participants’ insulin sensitivities, cholesterol ratios, blood pressure levels etc. all seem to improve after a few weeks on IF. Intermittent Fasting is also an eating pattern that is helping many people to become leaner and more muscular than ever before.

These improvements in health parameters seem to validate the thrifty gene theory which argues that, because are genome was likely selected in the late Palaeolithic era (50,000–10,000 BC), humans’ metabolisms are designed to operate under conditions of feasting and fasting rather than enjoying constantly available food.

Despite intermittent fasting looking fantastic in theory, it may be an impractical eating regime for young people and athletes with fast metabolisms. Cramming massive amounts of calories into only a few hours will prove very difficult unless your appetite is enormous.

It’s also worth noting that there have been no long term trials done on Intermittent Fasting and there is a lot we, modern humans, don’t know about it. There are many other lifestyle variables for young people to look at if they want to become leaner, more muscular and healthier before having to decide whether or not Intermittent Fasting will suit their lifestyle.

How do you get enough calories?

Most teenagers have considerably faster metabolisms than adults do and therefore need to consume more calories each day - young sportsmen and athletes will need to eat considerably more. If we assume that an average teenager needs around 3000 calories a day, and a young athlete may need as many as 5000 calories, then it becomes very difficult to eat the amount of food needed to supply these calories in an intermittent fasting eating window.

To illustrate this difficulty let’s look at the format of two popular Intermittent Fasting structures, ‘The Warrior Diet’ and ‘Lean Gains’, and consider how you could eat 3000 plus calories on these diets:

Ori Hofmekler’s ‘The Warrior Diet’:

The Warrior diet basically consists of fasting throughout the day and then eating one very large meal in the evening. Athletes are encouraged to eat low glycaemic fruits and vegetables along with light proteins such as egg whites and yoghurt throughout the day to help muscle recovery and to encourage detoxification.

As is meant to be the case on the Warrior diet, the raw fruits and vegetables and proteins like egg whites are catabolic foods meaning that they need more calories to be used by the body than they provide. These foods, therefore, will not help young people to reach their high daily calorie goals, all calories will have to be consumed within the feeding window.

As far as I can see, it’s going to be practically impossible for anyone aiming to eat 3000 plus calories a day to do this in basically one meal. You would have to focus your meal on extremely calorie dense foods like fatty meats and thick cream and then would have to fill up on low fibre starchy carbs like rice or potatoes so as to avoid fibre taking up space in your stomach. You will likely feel sick from the massive quantities of fat you’re eating well before you reach your 3000 calories.

Even if you don’t feel sick, the problem with eating so many calories in one meal is that, unless you have an enormous appetite (granted you will be extremely hungry after the fast) you are going to become uncomfortably full before you reach your calorie goals. You would have to completely disregard Ori’s advice to have a large salad to break the fast and to eat vegetables with your meal – you won’t be able to afford to waste stomach capacity with these healthy high fibre low calorie foods.

Martin Berkhan’s ‘Lean Gains’:

A more practical Intermittent Fasting option for someone needing to consume a lot of calories would be to follow Martin Berkhan’s Lean Gains diet structure.

On Lean Gains men generally fast for 16 hours from 9 pm to 1 pm the next day and women fast for 14 hours from 9 pm to 11 am, an eight hour and 10 hour eating window respectively. Men would therefore probably have to eat three 1000 calorie meals, maybe from 1 until 2, 4 until 5 and 8 until 9, to meet their calorie goals.

This may sound Ok but, whilst young people have fast metabolisms, not everyone is going to have the appetite to comfortably eat 1000 calories in a sitting, let alone have room to do it again in a couple of hours time. Whilst women have two hours more in which to fit in their meals most women have slightly smaller appetites than men so they will probably feel equally full. Obviously the situation will be much worse for active teenagers who may need to eat 5000 plus calories.

Having said this, I know that these diets work very well for many people and I'm using them as examples to undermine them. Martin Berkan clearly says on his website that he has no problem at all with teens eating breakfast and Ori says that the Warrior diet can be done eating two meals a day if this suits the individual better.

There are also other Intermittent Fasting structures you could try – ‘Eat Stop Eat’ for example – but, as far as I can see, the same problems as the above will apply. It is always going to be difficult to cram a massive number of calories into a small eating window when your stomach capacity is only so big…

Too much appetite suppression?

Many people comment that Intermittent Fasting is great for curbing their appetites. This is mainly because during the fast insulin levels and leptin levels drop way down and, once you have gotten accustomed to the eating pattern, you won’t be constantly told by Ghrelin, an anticipatory feeding hormone that makes you feel hungry, to eat every couple of hours.

This is great if you are an overweight middle aged adult whose appetite regulation system is out of whack and is telling you to eat more than you need every day. For someone trying to eat a high calorie diet it is going to become more difficult if you aren’t receiving reminders to eat from your stomach.

The end result of this is that there is a very real chance that you won’t be reaching your daily calorie needs when doing Intermittent Fasting. Maintaining a constant calorie deficit will make it very difficult to build muscle, will negatively affect your metabolism, may cause blood sugar problems like hypoglycaemia, and will make you feel irritable and depressed. In the long run, if calorie restriction does work, you may well add a few more years to your life though…

An uncomfortable eating window!

What you’re going to find on an IF eating regime, let’s take ‘Lean Gains’, is that you are uncomfortably full for eight hours of the day, 1 pm to 9 pm. If you like the shift between feeling empty in the morning to feeling extremely full in the afternoon then this diet may be for you, but I expect many would prefer to space their high calorie meals out so as to have a more comfortable period when they’re not digesting in between meals.

Is Intermittent Fasting Realistic For Teens?

It may be that a standard Intermittent Fasting eating regime will not suit a young person’s lifestyle well. Below are three examples of situations in which I imagine there would be difficulties, I’m sure you can imagine others as well:

1) Sport:

Most teens and college students play organised sport most, if not all, days of the week – having 2000 calories of meat, vegetables and potatoes, for example, in your stomach is not going to help your performance in a late afternoon rugby match! Equally, performing in the middle of a fast may suit some but many will find they lack energy and their performance levels drop.

Clearly the situation would be even worse for professional athletes. Many find training on empty to be an invigorating experience, but if your livelihood depends upon it I would stick to performing in a fed (not full) state.

2) School/ University lessons:

My personal experience eating a high calorie diet whilst doing Intermittent Fasting is that I feel unproductive during the feeding window, especially after the first massive meal. If you have not tried this approach, imagine taking a test directly after eating a Thanks Giving dinner – if you feel you would function well in this situation then intermittent fasting may well suit you, if not then you may struggle.

If I follow a meal pattern where you fast between 9pm to 1pm the next day, I find that I find that I can’t concentrate well when doing activities like reading or writing from about 11 pm through to 1 pm – this is not to say that I find it impossible to concentrate, my concentration is just slightly worse.

I have seen studies showing that, surprisingly, cogitative performance levels remain constant for up to 36 hours without eating, so moving away from a regular eating pattern theoretically shouldn’t affect your ability to concentrate on your daily tasks.

On the other hand, if you look at the dramatic increase in traffic accidents that happens every year during the fasting month of Ramadan, you may well draw different conclusions. Obviously the fact that strict followers do not take in fluids during the 12 to 16 hour fast should be considered as well.

Trying to Gain Weight:

The whole problem of getting enough calories will obviously be worse for a young athlete or bodybuilder who would need to consume well over their already high maintenance calories to gain weight. Most people need to add at least 500 calories a day to start gaining - that's 500 more calories to fit into your eating window.

There would be great pressure to substitute good food for junk food containing highly available refined calories. If you ended up doing this it is probable that IF would hurt rather than help your health. Whilst somewhat flawed, one Intermittent Fasting study indicated a decrease in glucose tolerance in people who ate 300 grams of refined carbs in their one evening meal whist doing IF.(1)

An alternative would be to do what people from Cross Fit interested in IF are doing, eat a very high fat diet. I am not against this but, if you try to make up your calories from nuts, as these guys seem to be doing, you are going to be messing up your omega 3 to 6 balance and will be consuming too many polyunsaturated fats overall in my opinion.

To be healthy, your diet would have to be based upon monounsaturated and saturated fats – this is fine if you can eat enough fatty foods to get your calories without wanting to chuck up!

More satisfying meals on IF?

One argument that proponents of Intermittent Fasting often make is that on an Intermittent Fasting plan you can eat large satisfying meals whilst remaining lean and muscular, whereas on a 6 to 8 meal a day eating plan you cannot do this without gaining weight.

It is true for many people that, unless you have a very small appetite, you will never be satiated after eating a meal that constitutes a sixth or eighth of your daily calories. Many say that IF has let them rediscover their joy of eating.

This argument, however, does not apply to young people and athletes who need to eat massive numbers of calories each day – if you split your calories into 3 big spaced out meals with a snack or four evenly spaced meals, you will still feel full and satiated after each meal. Only people with extremely high calorie needs will have to eat more than four meals a day.

Whilst satiation after eating may be a nice feeling, feeling absolutely stuffed is not a sensation many people like – cramming 3000 plus calories into a small eating window may well actually take the enjoyment out of eating because you will not be at all hungry for the second or third meals.

Improved relationship with food?

Another argument used in favour of Iintermittent Fasting is that it teaches you to eat to live rather than to live to eat. By all means see how it works for you, but if you’re constantly hungry because you’re not managing to eat enough calories I doubt you’re going to be able to appreciate the subtle flavours of your food when you finally get to eat it.

It’s also debatable whether you will be able to appreciate the second two meals in your eating window (assuming your doing Lean Gains) given you’ll still be full from the first.

Intermittent Fasting protects against diabetes, but it’s not the only way…

Recent research has confirmed the hypothesis that intermittent fasting improves insulin sensitivity and protects against diabetes in humans (2). With the rates of diabetes and obesity amongst young people in the western world rising in recent decades, the adoption an eating plan that protects against the development of insulin resistance, the common denominator in both of these diseases, should be encouraged.

However, whilst the results of recent intermittent fasting studies are impressive, there are many more obvious reasons for the rise in diabetes and obesity rates in young people that should be tackled before looking at meal timing: