What is the intermittent fasting diet, what are its weight loss results and what are the benefits?
There has been a lot of hype over intermittent fasting in the past few years, with some science backing, but what exactly is it all about?
YOU'VE probably heard someone talk about intermittent fasting, the 5:2 or the 16:8 diet by now.
But what exactly does it involve and should you try it to lose weight?
What is the intermittent fasting diet?
The intermittent fasting diet does what it says on the tin, but it can follow two patterns.
The first is eating just 500 calories two days per week, and eating normally (what you want) the other five days.
The second option is going 14, 16 or 18 hours a day without food, leaving you with a six to ten hour window to eat in.
The time in which your body starts to break down fat is after all digestion is fully completed and the nutrients have been taken from food.
This period after is called the post-absorptive state where excess fat will be stored in the liver for fuel stores, where it can be acessed to keep the body's functions ticking over when no energy from food is in the digestive system to use.
This is what happens when you sleep and when you are in a planned fasting period and insulin is low. Your body will need to take from fat stores even more whilst awake and fasting, as you'll need more energy to move around, which is when the weight loss occurs.
What are its weight loss results?
In a by The University of Surrey, researchers assigned 27 overweight people to either a 5:2 diet (fasting on 600 kcals two days a week), or a calorie restrictive diet (1400 kcals per day for women and 1900 for men) and the aim was to lose 5% of their weight.
The results showed it took the 5:2 dieters 59 days to achieve their 5% weight loss target, while it took the calorie cutters 73 days.
It also showed the 5:2 dieters cleared the fat from their blood post-meals quicker.
However, several people dropped out of the study and the focus group was very small.
Other undertaken on the effects of intermittent fasting at Utah's non-profit Intermountain Healthcare system showed that when compared with traditional calorie-cutting weight loss plans, people on intermittent fasting diets lost more weight.
They also seemed less likely to drop out of the diet than calorie cutters.
It seems to suggest weight loss is likely.
What are the other benefits?
- The main benefit is eating what you want on the non-fasting days, which might encourage dieters to stick to the plan.
- Some studies on animals have shown health benefits other than fat loss like lowering the .
- In the earlier mentioned by The University of Surrey, research showed blood pressure (systolic), was reduced by 9% on participants following the 5:2 diet compared to just 2% for the calorie cutters. A reduction in blood pressure will take pressure off the arteries and potentially reduce the chance of strokes and heart attacks.
- There is some to suggest it may have an anti-ageing effect.
Are there any negatives?
Fasting days are hard, especially to begin with, but it should get easier.
It could also impact your social life, if you let it.
The good news is you can plan around it on the 5:2 and choose days when you're staying in, or on the 12-14 hour daily fasts you could start eating later that morning to counteract your later evening meal with friends.
It does take more planning though and allows for less spontaneity.
Although studies seem to be positive, it is not yet clear whether there will be long-term effects, or whether it's likely to encourage eating disorders.
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Studies also tend to focus on overweight people, so whether it is as effective on those in the more normal weight zone is unknown, according to , a research dietitian with the Prevent Breast Cancer unit at the Manchester Breast Centre in the UK.
Studies always have drawbacks and it's often hard to completely accept results especially when you're relying on humans to control their diets and admit exactly what they are eating.
The University of Surrey research was also on a very small number of people.
It would need to be extended to make it more reliable.