When people think of intermittent fasting, they tend to think of the 5:2 diet, where people cut to a mere 500 calories on two days per week.
But anyone who's ever tried it - or indeed had the displeasure of being in the general vicinity of someone who does - will be au fait with the plan's draw backs.
Fast days are often plagued with hunger pangs, loss of energy and teenage mood swings. These undesirable side effects not only make the diet difficult to stick to, but could ruin the lives of your friends, family and colleagues.
The solution, according to Krista Varady - the author of The Every Other Day Diet, is simple: fast more often.
And she would know. The authority on intermittent fasting, Krista has worked on studies for more than 10 years and overseen trials on around 600 people (not to mention on a whole load of mice beforehand).
She featured on Michael Mosley's 'The Power Of Intermittent Fasting', the BBC programme which first popularised intermittent fasting back in 2012 - and saw the subsequent release of 5:2 diet plan.
But, as Krista reveals, there is currently no scientific evidence to support the 5:2 diet. All of the studies are based on the notion of intermittent fasting - ie cutting calorie intake everyotherday.
"I was asked to write the [Every Other Day] diet book five years ago," Krista reveals. "But I pushed back because wanted to run more studies. I wanted the diet plan to be comprehensive and able to address questions people may have. But then the 5:2 diet came along - claiming that all of the research pertained to 5:2."
Putting it bluntly, she says: "I got scooped".
The Every Other Day Diet works - and there is lots of scientific evidence as proof, just ask Krista - because it allows your body adapt to a 48-hour eating pattern.
Restrict your intake to 500 calories every other day (eating whatever you wish on non-fast days) and you could lose up to 2lbs per week, she claims.
You claim dieters will eventually not feel hungry at all - can you elaborate?
During our clinical studies, we measured hunger hormones (which regulate appetite and fullness).
Nowadays we've lost the capacity to recognise these signs, fasting corrects the hormones and we relearn what hunger and fullness feels like. Personally, I don’t think our bodies want to eat constantly throughout the day.
The body adapts to a 48-hour eating pattern and gets used to eating less. But the randomness of the 5:2 diet (with people picking and choosing random fast days) makes it more difficult for the body to adjust.
How do more fast days (seven per fortnight) fit into the average person's lifestyle? Weekends are generally rather sacred, are people able to stick to the diet?
It can be difficult to fit The Every Other Day Diet into your social life. While we recommend that people have a 500 calorie meal at lunch, it is possible to move that meal to the evening and still reap the same health/dietary benefits.
People tweak the diet in a way that works for them - there is no hard and fast rule. You can do two consecutive feast days, if need be. We want the diet to be flexible.
Of course, sometimes fast diets simply won't suit an individual's lifestyle. And that means they may have to find something else.
But I would say to give it a month before you quit, because the first week is always tough. 90% of our study participants stuck to the diet throughout the observation period, 10% drop out in first two weeks.
You recommend that people eat their 500-calorie allowance in one meal - why is that?
We recommend that people consume their calories in short space of time. Simply because if you spread them out there is a higher risk of miscounting calories - People think they are eating 500 calories but really they’re eating 900 and they wonder why they’re not losing weight.
Personally I can’t eat my meal in the evenings as I can’t get through the working day without eating, so I recommend people have
Of course people tweak the diet in a way that works for them - If you do lose weight by splitting up calories into smaller meals, that's great too.
Will dieters experience mood swings on fast days?
After the first week people's mood should improve and crankiness should disappear. WE need to conduct more studies to find out excatly why this is - but I think it may be down to low blood sugar.
Calories are where we get our energy from, so can you still exercise on the diet?
Yes, you can exercise.
We analysed a group of dieters at our research centre, who exercised 3 times a week. We also let people choose whether to exercise on feast or fast days, and they chose equally.
During the first week participants reported low energy, but it bounces back. Some people even report more energy on fast days.
It's actually advisable to exercise because you lose more weight if you do so - your muscle mass will stay high and, as a result, so will your metabolism.
Participants also tended to lose more weight if they exercised in the morning, before eating. Then when their post-exercise hunger surge came (when the body is rebuilding) they would eat their 500-calorie meal. If you exercise after eating, you still get your hunger surge and are more likely to cheat.
If dieters are allowed to eat as much as they like on non-fast days, can they really lose weight?
Surprisingly one of our main discoveries was that people can’t binge on feast days when following The Every Other Day Diet - people can on 5:2 because there is no pattern.
I think it may be related to stomach shrinking or people getting in touch with their fullness cues, but we have to carry our more tests.
I guess it's kind of a trick: we say ‘eat whatever you want’ but in truth people can’t do it.
You say that dieters choose whatever food they like on fast days, does this hinder weight loss?
In one study we split our participants into two groups: on fast days we gave group one a high-fat diet (cookies, lasagne etc but with smaller portions) and we gave the other group healthier options.
We found that both groups still lost weight and saw equal health benefits (lower blood pressure, cholesterol, insulin and glucose) and interestingly the high-fat group were less likely to cheat, as they felt more satisfied with their food.
I’m a nutritionist so I still want people to eat healthily, but we want to make the diet as accessible as possible. Anyone can start the diet, all they need to manage is portion control - not go out and buy a whole new load of groceries.
At our research centres we have weekly dietary and behavourial counselling to guide people towards a healthier option, educate them in nutrition and discuss weight issues.
The ultimate goal is less processed food and increased fruit and vegetables intake.