The 5:2 Diet –
The Good, The Bad and the Ugly
“Have you heard about that NEW fasting plan everyone’s doing?”
“What about this 5:2 diet then? Surely that can’t be healthy?”
“I’m thinking about that diet where you fast two days a week and eat whatever you like the other five. Apparently it works like a charm.”
As a trainer, you can imagine I’m inundated with questions from clients regarding new diet trends and fads on a daily basis, and when the 5:2 diet first came along, my question-fielding capabilities were tested to epic proportion.
Even if you’re not involved in the fitness and nutrition industry, you’ve probably heard of the 5:2 diet. In fact, unless you’ve had your head buried under a rock the past year, you’ll know about it. And even if you have had your head under a rock, I’ll hazard a guess you’re at least vaguely familiar with the concept – it’s been that big.
As with any diet that comes along, it can be difficult to judge whether it’s all hype, mass marketing, and clever ad campaigns, or whether there is something to it.
So here’s where I step in. In this article, I’ll uncover the good, the bad and the ugly on the 5:2 diet, while aiming to keep a neutral perspective.
What Is It?
The 5:2 diet as most people know it, was the brainchild of Dr. Michael Mosely, who released the original 5:2 diet book – “The Fast Diet: The Secret of Intermittent Fasting – Lose Weight, Stay Healthy, Live Longer” in January 2013. This followed on from the BBC’s Horizon program “Eat, Fast and Live Longer” which Mosley presented, first broadcast in 2012.
The premise of the diet is remarkably simple:
You eat a very low number of calories two days per week, and eat what you like on the other five. In fact, here’s the exact blurb from the book’s Amazon page –
This revolutionary new approach to weight loss really is as simple as it sounds: you eat normally five days a week, then for just two days you cut your calories (500 for women, 600 for men).
Scientific trials of Intermittent Fasting have shown that it will not only help the pounds fly off but also lower your risk of a range of diseases, including diabetes, heart disease and cancer.
Dr Michael Mosley, the medical journalist who first alerted the world to the Intermittent Fasting phenomenon, presents the fascinating science behind the 5:2 diet. Mimi Spencer, award-winning food and fashion writer, explains the practicalities of how to go about it. (1)
Got that? Good. It’s straightforward enough, so let’s start the dissection …..
Most regular people following the 5:2 diet will be eating in a calorie deficit, which is vital for weight loss. A calorie deficit simply means burning more calories than you consume. By adopting the two fast days per week of just 500 to 600 calories, you’re automatically cutting out almost two days’ worth of calories. You might be thinking that by doing these fast days, you’ll be ravenous on your feast days, and simply consume a much greater calorie intake to make up for the fast days. Chances are however, you might eat a little more, but probably won’t go too overboard. The easiest way to look at this is with an example.
Let’s take a woman who needs 2,500 calories per day to maintain their weight.
Following a normal, non-fasting eating plan, she eats 2,500 calories every single day. That’s a total weekly calorie intake of 17,500.
Following a fasting plan, she eats 500 calories two days per week, and maybe a little extra, say 2,750 on feast days. That totals 14,750 calories each week.
This makes a deficit of 2,750 calories over a weekly period – enough to lose around 1 pound every nine days or so.
As discussed above, the fast days aren’t complete fasts – you can have 500 to 600 calories.
I’m a fan of this, as I think it firstly makes the diet a little more manageable, and secondly, gets people to focus on nutrient-dense, healthy, filling foods at least two days of the week.
According to Mosely – “The basic principle is to eat foods that are high in protein and fibre, as these are the most satiating. That means fish, meat, vegetables” (2)
If you’ve got 600 calories to play with, what are you going to eat?
600 calories could be a Mars Bar, a pack of Hula Hoops and a milky coffee. Or it could be –
– 1 chicken breast, 2 boiled eggs, an apple, a protein shake, a serving of mixed berries, and a huge salad with spinach, kale, cucumber, celery, tomatoes and carrot.
Both the same calories, but let’s face it, when you’ve got a whole day to get through with such a meagre allowance of food, even the most ardent of junk food fanatics is going to struggle to pick option one. 99% of people will opt with the much larger (and much more nutrient-dense) option two.
No Product Sales
Besides the associated recipe book, there don’t seem (to me at least) to be any sort of promoted supplements alongside the diet. I’m far from an anti-supplement guy (check on my blog on the five supplements you should give a crap about – http://www.healthylivingheavylifting.com/the-5-supplements-you-should-give-a-crap-about/ ) but my ulterior motive detector reaches full force whenever I see a diet partnering with a supplement company or workout DVD.
You might be thinking that a lack of food on your fast days will lead to you feeling at death’s door, with hunger pangs from hell. You might be surprised to hear then, that fasting can actually help to control hunger.
Trainer Anthony Mychal argues that your body is adaptable, and we only really get hungry at certain times because we have a set internal body clock, that we’ve programmed to expect food. All our lives we wake up and have breakfast. Between breakfast and lunch we have a snack. Lunch usually falls five to eight hours after waking. We have dinner after roughly the same interval again, possibly with another snack between. Day in, day out we repeat this process, leading to our bodies expecting food at certain times. (3)
Within a few weeks however, your body will adapt to its new regime, and fasting will become the norm, meaning no more hunger pangs.* (Keep reading for more pointers on this a little later on.)
In his experiment with intermittent fasting, sports nutritionist Dr. John Berardi notes that learning how to feel hungry and not “freak out” can also be highly beneficial. Often, you feel hungry, but you don’t actually need food – it’s just a craving, or feeling of boredom that’s making you feel a little peckish. Hunger also peaks and diminishes, meaning you can feel ravenous five or six hours after your last meal, but give it an hour or two, and you probably feel okay again. (4)
The 5:2 diet is pretty much idiot-proof.
Sure, you do need to count calories on your fast days, but I’d predict most folks will fall into a pattern, eating more or less the same foods each fast days, so once you’ve got to grips with counting calories for the first few weeks, you needn’t bother from then on in.
Plus, counting calories is incredibly easy with sites and apps like MyFitnessPal. http://www.myfitnesspal.com/ I’ve even had some clients tell me it’s so simple their 7 and 8 year old kids have set up the accounts for them and helped them track their intake.
So far, s’all good with the 5:2 diet. So what could possibly go wrong?
Not for Everyone
Just like any diet under the Sun, be it calorie-counting, Paleo eating, low-carbing, the Zone, Weight Watchers, etc. the 5:2 diet will not suit everyone. There’s more on this again in a while with a specific reference to athletes, but for now, even looking at non-exercising the general public, it won’t suit every person’s lifestyle and preferences.
Despite Mychal and Berardi both suggesting your body will adapt to a different feeding pattern over time, there will still be a phase of adaptation where you feel pretty damn rough.
That could be a week, it could be two, it could be a month. Now, this again isn’t necessarily a bad thing – any type of dietary changes will incur some sort of adaptation phase, but I’d argue that due to the fact you’re following different eating patterns on different days, the 5:2 adaptation phase will be longer than that of a diet where you’re doing the same thing day in, day out.
No Monitoring of Calorie Intakes
On the “feast” days, the idea is that you eat sensibly, but don’t stress over counting calories.
In the beginning of the diet, you’ll probably be absolutely fine, and I very much doubt you’ll go too high on your feast days. As demonstrated in the example earlier, most people will eat slightly more than usual (or more than maintenance level) on the feast days, but this isn’t an issue due to the very low intakes on the fast days.
There will be a certain type of person however, who sees the feast days as a challenge, and almost goes out of their way to eat as much as possible.
Likewise, many people simply aren’t aware of calories, or how much they consume.
A study from Lichtman et. Al found that obese subjects grossly under-reported their calorie intake, and over-estimated their energy expenditure. (5) A 2007 study from the “Journal of the American Dietetic Association” further showed that under-reporting food intake was a major contributor to gaining weight. (6)
I believe that this video (coincidentally also taken from a BBC documentary) shows exactly why monitoring your calorie intake, regardless of what type of diet you’re following, is absolutely critical
Bad for Athletes/ Performance
One of my favourite quotes regarding nutrient timing and workout nutrition is from Alan Aragon –
“The first law of nutrient timing is: hitting your daily macronutrient targets is FAR more important than nutrient timing.
The second law of nutrient timing is: hitting your daily macronutrient targets is FAR more important than nutrient timing.” (7)
In essence, nutrient timing really doesn’t matter. You can eat every few hours, just once or twice a day, or at exactly 27 and a half minutes past each hour – it really doesn’t matter.
That is, until you come to discussing performance and high level athletes.
It’s a bit of a myth that you need to eat within 30 minutes of a workout, or you need fast-digesting carbs and protein pre and post training for optimal performance. But workout nutrition goes on a continuum. Those partaking in low-intensity activity needn’t worry one iota about workout nutrition, and let’s face it, if you’re training two to three times per week while following 5:2, you’ll probably make sure your fast days coincide with your rest days from the gym.
Even harder training folk, potentially involved in bodybuilding, strength sports or recreational fitness have at least two rest days each week, which can be placed on fasting days, with little impact on their weekly schedule.
But what about athletes training every day, or some days twice per day?
These guys are screwed if a match, or a crucial training practice falls on one of their fast days. Therefore, I will categorically state that the 5:2 diet is a very poor choice for anyone serious about maintaining optimal performance on a regular basis. On days where you’re performing multiple sessions, the number one goal of your workout nutrition and timings should be to replenish glycogen stores between these workouts, meaning a high carbohydrate intake (relative to total daily intake) after the first session and before the second, along with adequate protein consumption is vital. (8)
Irregular Fasting Pattern
Once again, I’ll state that I have no issue with fasting, or very low calorie days. They don’t crash your metabolism, lead to muscle loss, or cause a starvation response, as many popular myths seem to perpetuate. Plus, as noted above, your body does become accustomed to whatever you throw at it with regard to meal timings.
However, by fluctuating between fast and feed days, you don’t give your body much time to get used to it. I know when I tried the Lean Gains style of intermittent fasting (where I broke my fast at 2pm every day) it took me two to three weeks to get used to not eating for the first eight or nine hours of waking.
This is all well and good if you’re fasting for periods every day, but when you’re only doing it twice a week, you’re not fasting frequently enough to adapt and quell the cravings and hunger pangs.
Additionally, research has shown that an irregular meal frequency could have negative effects. A study published in the “American Journal of Clinical Nutrition” found that an irregular feeding pattern had negative impacts on TEF (thermic effect of food,) insulin sensitivity and cholesterol levels. (9)
It’s Not New
This is more a personal gripe that I have with the publicity and media hype surrounding the book and diet.
The Amazon blurb reads –
“Dr Michael Mosley, the medical journalist who first alerted the world to the Intermittent Fasting phenomenon”
First up, it’s not a phenomenon – it’s a way of eating. We fast while we sleep every single night, and other cultures have been practicing fasting style diets for centuries. Those of us in the health and fitness sphere have also been well aware of such diets due to the emergence of books like Brad Pilon’s “Eat. Stop. Eat,” Ori Hofmekler’s “The Warrior Diet” and Martin Berkhan’s Lean Gains site.
It’s also not anything magic or revolutionary. To lose fat, you still need a calorie deficit, regardless of whether you include periods of fasting or not.
Perhaps this bit isn’t so objective, but I thought it was worth including. If someone tells you they have the latest breakthrough, or the new best method for torching fat and losing weight, they’re probably trying to sell you something.
So far, it’s pretty even, but this is where the doo doo hits the proverbial fan.
If weight loss and caloric restriction were a good point, then how can weight gain make it onto the ugly list?
It’s fairly simple, and relates back to the calorie example right back at the start of this piece.
Take the same woman with a maintenance calorie intake of 2,500 per day, or 17,500 each week.
Let’s plan her two fast days of 500 calories each first, giving her 16,500 calories left to play with over five days to make sure she stays in a deficit, or at the very least, doesn’t splurge over into a surplus.
I stick by my original point that any sensible person, while not counting calories, probably won’t overeat on the non-fasting days. At least in the beginning.
Unfortunately though, from my personal experience with working with clients, many people don’t adopt a sensible, moderate approach when tackling a diet. By its very nature, 5:2 is fairly extreme. This can lead to people thinking they’re so restricted on their fast days, that they decide to go all out on the feast days, and almost view them as a challenge, shovelling down as much food as they can.
This initially started out as pure speculation, just from my experiences. However, when I decided to write this blog, I posted on my Facebook page – https://www.facebook.com/HealthyLivingHeavyLifting?ref=hl asking for peoples’ experiences of 5:2 and got the following replies –
“A guy at work has (done this) since 1st jan. Honestly can’t notice the difference yet, but on his normal days he has a Gregg’s steak bake, pizza slice and tuna mayo baguette just for lunch, which probably doesn’t help.”
“I just think people binge to excess on the 5 days and aren’t getting the right fat, protein and carb intake”
“I found it easy enough after the first few weeks and the twice weekly fast helped keep me on track and made me pay attention to what I was eating, I dropped about 2 stone over 6 months which was fairly sensible going. Unfortunately I started taking the p*ss after that and letting myself get away with more on my normal days, didn’t put anything on but fat loss stalled.”
“I had to be strict on first few days back on food to avoid binging but found I was to moody and snappy on fast days”
The more severe the restriction, the more severe the rebound. This is why I’m such a fan of the flexible dieting approach, where nothing is off-limits, you just adopt a moderate approach, but allow yourself small portions of anything, as part of an overall balanced, nutrient-dense diet.
Much like people overestimate how many calories they burn from exercise, which leads to thinking they can eat a hell of a lot more than they can actually get away with, fasting leads to a similar mind set People forget on the fast days they may actually only be eating 1,000 to 2,000 calories fewer than usual, which actually isn’t a lot in the grand scheme of things. Yet in the general publics’ minds, two fast days warrant five days of massive eating.
I wrote an article for the FitPro Client website on how a simple weekend of indulgence can ruin a week’s worth of fat loss progress. If you can do that much damage in two days, imagine what you can do in five.
Bad Relationship with Food
This is my number one pet peeve with the 5:2 diet.
By employing this idea of “eat or don’t eat” you’re effectively saying that fasting is good and eating is bad. It’s the same as having the idea that you can only eat “clean” foods, and that anything processed is bad. Or that you’re either “on” a diet and suffering from the restrictive aspect of it, or “off” a diet and completely letting everything go, falling into a cycle of restriction and binging.
Here’s my second most-read blog ever, detailing cheat meals and a poor relationship with food –
Here are a few more quotes from the good folks over on the Healthy living Heavy Lifting Facebook on their experiences and observations of following the 5:2 diet –
“ I have heard a lot of horror stories about peoples’ “friends” doing it, then reducing the calories, then going 4:3, 4:4, 3:4 etc
“all these diets are tantamount to pro-anorexia. “want to lose weight? just don’t eat for a few days”. terrible idea.”
“My mother-in-law is doing this and I strongly disagree with the diet. On the 2 days where u eat your low amount of calories she basically starves herself and lives on dried apricots and maybe a plum or some other fruit.”
And herein lies my biggest issue with the 5:2 diet, and what I consider to be the “ugly” aspect.
Anything extreme (and in the view of the general public, a diet that encourages almost complete food avoidance for over 25% of the time is extreme) encourages a poor relationship with food. Can you really tell me that the average person isn’t going to effectively binge on those five feeding days each week?
The Wrap Up
I’ll finish this with the question I got so regularly that it prompted this article, and the answer I always responded with –
– “Is the 5:2 diet good?”
– It Depends
If you find that you can lose weight on the 5:2 diet, you feel pretty much okay on the fasting days, and never get the urge to binge on the other five days, then it will work for you, and is absolutely a good fit.
If however, you fall into the category of “so hungry you’d gnaw your own arm off” when fasting and go into “eat, eat, eat” mode on the fast days, I’d argue it’s not for you.
If you’re interested in the benefits of fasting, but want something a little easier to adhere to and better for maintaining performance, yet still with the potential benefits of fasting, I’d recommend something more akin to the LeanGains protocol, where you fast for 16 hours per day and eat all your calories in an eight hour window. A sample day would look something like –
7am – wake
8am – 12pm – calorie-free drinks (tea, coffee, water, etc.)
12pm – 1st meal (containing around 25% of your daily calories)
5pm – 2nd meal (containing around 25% of your daily calories)
6pm-7pm – Train
8pm – 3rd meal (containing around 25% of your daily calories)
Give it a whirl and let me know how you get on.
References5:2 diet, diet myths, fasting, fat loss, if
Sign up to the newsletter for regular updates