The 5:2 Diet – I’m not buying it

Last night, a popular current affairs show on Australian television ran a story about the 5:2 diet. Credited to BBC science presenter Dr Michael Mosley, the 5:2 diet is an eating system. Simply put, you stick to a normal, sensible diet for five days each week. For the other two days, you restrict calories to a quarter of your normal intake. You don’t need to be a dietician or science guru to understand why the system works. It simply a calorie restriction diet. My problem is that it is backed up what sounds like solid science about how we evolved from hunter-gathers. But it only sounds like solid science – much of what Mosley says has been debunked.

The full story can be watched below but I wanted to focus on a couple of specific things that came from the story.

The Cave Man Argument

Here’s a quote from the story.

What researchers say is that we are decedent from a long line of cave men and cave women. So the tradition of feast and fast is built into our genes.

I discussed this recently when I suggested Beware Science – or at least purported scientific experts. In that post, I looked at the paleo diet and its scientific basis.

Our “tradition” of feating and fasting had more to do with food scarcity and availability than anything else. And, as hunter-gathers, humans and their forebears were more active than most people in Western cultures. Even on a day when I run several kilometres I’m fairly certain I cover less ground that my ancestors.

Humans are not “evolved” to eat specific foods or to eat according to certain regimens. We are omnivores and, if we learn anything from the fossil record of our ancestors, we eat whatever we can get our teeth into that does;t kill us.

Fasting Makes you Smarter

According to the story, there’s some “groundbreaking research” which has found that starving the body fuels brain activity.

It dates back to when we were cavemen. In order to catch food, a starving caveman had to be sharp and agile.

There’s an inherent problem in that statement. Starving humans are slower and weaker. It takes less than a month of starvation for a human to become seriously ill. Now, the statement sounds reasonable – we’re hungry so we’re desperate for food. Because we’re low on energy we have to hunt smarter. As a result, our brain activity needs to increase or improve so we can hunt better.

That suggests that our ancestors could not plan ahead and hunt before they were starving or in a forced fast.

The supposition made in the story doesn’t seem right to me.

There’s also the claim on “ground breaking” research being done on mice that has shown an increase in the “ability of mice to remember and learn, and decreases their risk of dementia”.

The words “ground breaking” and “on mice” don;t fill me with confidence in the conclusions. When research is at that level, it is still in its infancy and a long way from validation in human subjects.

I’m not saying it’s wrong but it’s probably premature to hang your hat on it as validated scientific fact.

Wasted Exercise

The last thing I wanted to consider is the claim that

when it comes to exercise, Dr Mosley’s view is that those hour-long gym workouts are 57 minutes wasted

52-dietHis supposition is based on the hunter-gather life being made up of long periods of walking interspersed with short bursts of intense activity when humans were either hunting or fleeing danger. This one is pretty close to the mark in my view except that hunter-gathers were active a lot of the time.

Our modern lifestyle, based around a centralised society and, largely, sedentary lifestyle. In contrast, our ancestors were probably stronger and had better endurance because they were more constantly active than we are.

Well planned and correctly executed exercise programs are beneficial. They help increase our bone density, flexibility, balance, and myriad other physical factors. They also affect our mood.

Mixing endurance activities such as running, cycling or swimming with high intensity bursts of activity such as sprinting or lifting weights is proven to be effective in boosting metabolism and increasing fitness.

If the story had said that a mixture of endurance and high intensity activities is more beneficial than simply carrying out an aerobic activity at one pace was a better system then I’d agree.

It’s About Balance

I understand why the 5:2 Diet is popular. it’s a simple eating system than most people can buy into as it doesn’t force you into buying special foods or supplements. You can simply do it by following your current eating pattern and just modifying things for two out of every seven days.

But it is simply a calorie-deficit diet – the same sort of thing people of have been using for decades. Weight Watchers, Jenny Craig and other programs have all been about calorie-deficit eating systems. they just package them in different ways.

The 5:2 Diet looks to be a more sustainable system than many of the others. But it doesn’t give you carte blanche to nine on the other five days. It’s still about a balanced diet and activity program.

If you want to pay for Dr Mosley’s book and get into the 5:2 Diet that’s fine. Like I’ve said before, find what works for you. But don’t just buy it because it’s scientifically supported.

What Do I Do?

My system is simple. I track calories using MyFitnessPal and try to say under my calorie goal for each day. On days when i exercise, that goal is higher than rest days.

Simple, calorie deficit eating. I don’t buy special foods. I eat pretty much what I want but in moderation.

Story link: The 5:2 Diet Phenomenon [Sunday Night – Seven Network]

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