First change when you eat, not just what you eat.
s the author of The Fast Diet I am, naturally, extremely interested in anything to do with intermittent fasting. Recently I came across new research which suggests that a good way to keep healthy and the weight off is to change when you eat rather than just how much you eat.
My particular approach to intermittent fasting is one I invented a few years ago and which I call, the 5:2 diet. On this diet, instead of calorie restricting every day, you cut your calories two days a week. That means cutting back to around 600 calories twice a week if you are a man, 500 if you are a woman.
I've had thousands of emails from 5:2 enthusiasts and many have said that the reason they like the 5:2 approach is because it is so simple, plus they find it psychologically easier to cut their calories twice a week rather than being constantly on a diet.
As one woman put it, who had lost 20kgs, "I have the will power to say, "I won't have that doughnut today, I will have it tomorrow. Then tomorrow comes and maybe I have it, but often I don't."
The other thing people like about the 5:2 approach are the health benefits they get from short periods of fasting.
It is only very recently that humans have lived in an environment where they can eat any time they want. Our remote ancestors, like most animals in the wild, would have had to survive during periods of feast and famine. Our bodies are not designed to cope with constant calories.
Part of the problem is that your body needs down-time. It is only during those hours of the day or night when you are not eating that your body gets on with essential repairs. It's a bit like keeping your house in good shape. If you spend every spare moment buying food, cooking, eating and then washing up, you are not going to have time to repair the guttering, replace broken light bulbs and remove worn out sofas. At a cellular level the equivalent of the spring-clean normally occurs overnight, when you are having a short fast.
Although lots of people have told me they find cutting their calories two days a week relatively easy to do; others have struggled. So I was intrigued when I came across research done at the Salk Institute in California where they are looking at a different form of intermittent fasting: instead of cutting your calories you simply restrict the hours within which you eat.
In their most recent study researchers subjected hundreds of mice to different lengths of daily fasts, ranging from 12 to 15 hours.
What they found was the mice who fasted for at least 12 hours a day remained healthier and far slimmer than those who ate the same number of calories, but spread out.
The study was done in mice, but human studies are now underway.
A 12-hour fast isn't as bad as it sounds because most of it can be done while you are sleeping. On the Salk regime you could have breakfast at 8.30am, a light lunch, then an evening meals at 8pm. Assuming you were done by 8.30pm, that would give you 12 hours before your next meal.
Another option would be to skip the evening meal or have a very light one.
In a recent study researchers at the Institute for Clinical and Experimental Medicine in Prague randomly allocated volunteers to a diet of 1,700 calories a day.
One group ate those calories as two meals: breakfast and lunch. The other group ate those same calories as six small meals, eaten at regular intervals throughout the day.
A very common dieting belief is that if you spread out your food into lots of small meals this will increase your metabolic rate, keep you less hungry and help you lose weight. Well, it turns out this belief is completely false.
Despite eating exactly the same food the "two meal a day" group lost, on average, 1.4 kg more than the regular eaters and about 1.5 inches more from around their waists. They also felt more satisfied and less hungry than those eating more regular meals.
Get more sleep
The average adult needs 7-8 hours sleep a night and probably gets closer to 6. There is an obvious connection between lack of sleep and over-eating. If you're feeling tired during the day you will find it harder to resist that bar of chocolate or bag of crisps. If you're feeling tired at night you are far more likely to reach for the booze and the crisps. Being overweight also means you probably snore and get bad quality sleep, which makes this a particularly vicious circle.
But how much difference would, say, getting an extra hour of sleep a night make? A while ago I got some volunteers, who normally sleep anywhere between six and nine hours, and asked them to take part in a study at the University of Surrey's Sleep Research Centre.
The volunteers were randomly allocated to two groups. One group was asked to sleep for six-and-a-half hours a night, the others were encouraged to get seven-and-a-half hours.
After a week we did some mental agility tests on them and took bloods. Then our volunteers were asked to switch sleep patterns. The group that had been sleeping six-and-a-half hours got an extra hour, the other group slept an hour less.
When our volunteers had finished their second week we repeated the tests.
We found that when our volunteers cut back on their sleep from seven-and-a-half to six-and-a-half hours' sleep a night most of their mental agility scores plummeted.
We also saw genetic changes which suggested they had become much more vulnerable to stress and weight gain.
So if you are getting less than seven hours' sleep a night and can alter your sleep habits, even a little bit, do. "Have a lie-in, it will help you slim" - that's the kind of health message that doesn't come along very often.
Eat more resistant starch
As we all know, piling your plate with carbs like bread, rice and pasta is not a good idea if you want to lose weight. It is better to cut back on these easily digestible carbs and replace some or all of them with vegetables or legumes, such as lentils, peas, chickpeas, beans. Unlike bread or pasta these are loaded with nutrients and fibre, which will keep you feeling fuller for longer.
Shaking off the pasta habit can be tough and one of the things I've found helpful was a Japanese invention called a spiraliser, a device that creates thin ribbons out of vegetables.
Courgettes, done this way, look and taste surprisingly like spaghetti, so you can have it with your Bolognese and have the illusion you are eating pasta, but instead you get all that veggie goodness.
On the other hand, if you are addicted to pasta there is a surprising way to make it less fattening and increase its fibre content. And that is to cook, cool and reheat it.
Like all carbohydrates pasta gets broken down in your guts and then absorbed as simple sugars, which in turn makes your blood glucose levels rise.
In response your body produces a surge of the hormone insulin to get your blood glucose back down to normal as swiftly as possible, because persistently high levels of glucose in the blood are extremely unhealthy.
A rapid rise in blood glucose, followed by a rapid fall, can often make you feel hungry again quite soon after a meal. It's true of sugary sweets and cakes, but it's also true for things like pasta, potatoes and white rice.
But what if you could change them into a food that, to the body, acts much more like fibre? Well, surprisingly enough, if you cook pasta and then allow it to cool it changes into something that is called "resistant starch".
It's called "resistant starch" because once pasta, potatoes or any starchy food is cooked and cooled it becomes resistant to the normal enzymes in our gut that break carbohydrates down.
So if you cook and cool pasta then your body will treat it much more like fibre, creating a smaller glucose peak and helping feed the good bacteria that reside down in your gut. You will also absorb fewer calories, making this a win-win situation.
One obvious problem is that many people don't really like cold pasta. So what would happen if you took the cold pasta and warmed it up?
When I asked scientists this question they said that it would probably go back to its previous, non-resistant form, but no-one had actually done the experiment.
So Dr Denise Robertson, from the University of Surrey, put some volunteers through three days of testing. On each occasion they had to eat their pasta on an empty stomach.
On day one they ate pasta, freshly cooked, nice and hot with a plain but delicious sauce of tomatoes and garlic.
On day two they had it cold, with the same sauce, but after it had been chilled overnight.
And on day three they ate it with sauce after it had been chilled and then reheated.
On each of the days they also had to give regular blood samples to see what happened to their blood sugar levels.
So what did happen?
Just as expected, eating cold pasta led to a smaller spike in blood glucose and insulin than eating freshly-cooked pasta.
But cooking, cooling and then reheating the pasta had an even more dramatic effect. It reduced the rise in blood glucose by 50pc.
Since we did that experiment a group in Sri Lanka have done something similar with rice. They found that if they boiled the rice with a bit of coconut oil, cooled it down, then reheated it in a microwave they could increase the levels of resistant starch in the rice roughly 15-fold.
A neat "cheat" and a good way to use up left-overs.
Chew your calories, don't drink them
Unlike food, the calories we consume in the form of drink don't fill us up, and some of the worst offenders are the treats you find in coffee shops which people fondly imagine are healthy. A Starbucks 16oz strawberry smoothie contains a whopping 300 calories and the equivalent of nearly 10 teaspoons of sugar. It would take you about two hours to walk that lot off. A 12oz orange juice comes in at a more modest 140 calories and 7 teaspoons of sugar, which is similar to a can of Coca Cola. Though there are a few more vitamins in an orange juice, you would be a lot better off eating an orange. Alcohol is also highly calorific, with a large glass of wine containing around 200 calories, similar to eating an ice cream.
Does that mean it is okay to drink diet sodas? Probably not. You might think that artificial sugars are harmless and they pass right through you, but a recent study found that in many people this isn't true. In 50pc of people their gut bacteria responds to a diet of zero calorie sugars by producing inflammatory factors that increase the risk of obesity. Research out of the University of Texas at Austin, where they followed 474 people for about a decade, found that diet soda drinkers had a 70pc greater increase in waist circumferences than non-drinkers.
What you really need to be drinking are natural zero calorie drinks, such as herbal tea and water. I drink lots of fizzy water with flavourings like lemon or lime juice.
Does it really help weight loss? Well a few years ago Dr Brenda Davy of Virginia Tech put 48 overweight volunteers on a diet, as part of which she randomly allocated half of them to drinking two glasses of water before each meal. Over the course of 12 weeks the water drinkers lost 2 kgs more than the non-water drinkers.
Eat more filling foods
One of the reasons that sweet sugary drinks, even "natural" ones like apple juice, help make you fat is because they contain very little fibre. As I explained above, to curb your appetite what you need are foods that your body will find harder to digest. The longer your body takes to break down and digest a meal, the longer you will feel full. That is why eating foods rich in resistant starches is a good idea. It also means you should be loading your plate with things like whole grains, vegetables, meat and "good" fats.
One of the great myths of recent time is that fat makes you fat. In fact it is the easily digestible carbs, like sugar, that are most readily converted into fat in your body. "Good fats" that will keep you full and reduce your risk of heart disease include nuts, avocadoes, olive oil and oily fish.
Adding more protein to your diet is also an excellent idea. I have Greek yoghurt or eggs for breakfast most mornings, rather than cereal or toast. It is yet another myth that eating eggs will raise your cholesterol levels.
There have been several massive review studies which have shown no association between egg consumption and risk of heart disease. The same is true of dairy fats, like yoghurt.
Eat only what you love
If it's bad for you, it had better taste good. Instead of grabbing that extra slice of cake which you don't really want - and adding a few hundred unwanted calories to your waistline -wait for something that you will really enjoy. I keep some dark chocolate in the freezer so when I get a craving it will melt slowly in my mouth.
n Keep good food close, bad food out of sight
A lot of our food choices are unconscious. A while ago I was making a One Show film where we asked volunteers to sit on a sofa and rate a movie. On the table in front of them were crisps, chocolates, fruit. What we found was that the volunteers ate whatever was nearest to them, with one guy munching his way through over 1,000 calories in crisps in less than an hour. Keep tempting foods in cupboards or out of the house entirely.
Another useful "cheat" is to spice up your food
That means adding in more herbs (rich in anti-oxidants) and perhaps pepping up your morning eggs with a blast of chilli. In a Danish study they found adding a gram of red chilli pepper, about 1/4 teaspoon, reduced cravings for salty, sweet and fatty foods and increased energy expenditure. I am a big chilli fan but if you are not used to it then I would start more gently.
Try to keep an honest diary of what you eat over the next few weeks
Studies show that people who keep an honest diary of what they eat and drink are more successful at losing weight and sticking to a healthy diet.
Next week you can read Michael Mosley's Cheat's Guide to exercise