At the end of 2019 fasting for weight loss as well as the benefit of fasted workouts hit the headlines thanks to two celebrity Jennifers. As a fan myself, I thought I’d take a look at the research.
Both Jenifer Aniston and Jenifer Lopez have revealed themselves as fans of fasting, but in very different ways. While Aniston does the intermittent fasting diet plan 16/8 (only eating for eight hours in the day), Lopez does fasted exercise first thing in the morning under the instruction of her trainer Dodd Romero.
I’ve spoken to the experts and found out all you need to know: from fasted workout benefits and whether fasted cardio burns more fat, to the side effects of intermittent fasting and what you can drink.
Intermittent fasting for weight loss
The 5:2 diet kicked off the popularity of intermittent fasting for weight loss in 2012, when the book the Fast Diet by Michael Mosley and Mimi Spencer was published. Towards the end of the decade the 16:8 had begun gaining popularity.
As well as weight loss, intermittent fasting can help regulate hormone levels and allow the body respond better to insulin, which together can aid fat loss. It also improves cell function and repair which is important for exercise recovery. Intermittent fasting can also lower the levels of bad cholesterol, boost energy and improve cognitive function.
The side effects of intermittent fasting
At first, it can make you feel tired and maybe even weak. It may be best to start with a larger eating window and shave off and hour a week.
While it has been proven to help prevent diabetes, for those already diagnosed it may not be suitable. Those considering it should consult their doctor.
Something to be wary of, especially if you’re trying it for the first time, is overindulging outside of fasting times.
Fasted workout benefits
Fasted exercise — usually undertaken in the morning before breakfast — is said to force the body to use stored fat for energy, which in time it will become accustomed to doing more often throughout the day. Studies also show it is likely to reduce blood sugar levels. Researchers from the University of Bath in England also found exercising on an empty stomach had the tendency to stop people overeating later in the day.
The side effects of fasted exercise
While burning the body’s stored fat may sound appealing, low carbohydrate levels in the body can make you feel tired and less motivated to train in the first place. It is also possible that you will struggle to train at a high intensity, so it is a good idea to do it on days when you’re exercising at a low intensity or not trying something new.
For both intermittent fasting for weight loss and fasted exercise, much of the research has only been done on men. One study done with women showed a negative effect on blood sugar levels, and some health professionals question the effect on female reproduction.
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