Fasting - should you be doing it?

Fasting - should you be doing it? 

Are you a woman?

Do you have a BMI under 30? (ie not medically obese)

Are you active? Do you exercise regularly?

 Then the science says NO 

If you start putting a bit of weight on in peri/post menopause it's very tempting to start a fad diet as you can start to get a bit desperate. (Yes, I'm calling fasting a fad diet.) But, what's the deal? Will you lose weight? Is it good for you in the long term? Is it going to improve your athletic performance? These are the answers you need.

Most active women are already on the edge of Low Energy Availability (they don't eat enough for the exercise they are doing). Fatigue and not feeling recovered between training sessions is a big sign you're under-fuelled.

 Back story 
Fasting has been around since the dawn of time - religious observance. (If your goal is to get closer to God then do it.)

Then came more science based reasons for doing it - middle aged, obese men with serious conditions like type 2 diabetes needed operations so they fasted to lose weight quickly. 

More present day are the various different methods: Fast 800, 12 hour or 16 hour windows, alternate day, 5:2. Hundreds of 'em!

Other benefits of fasting also came out of research: increased focus, autophagy (body clearing out old cell debris), improved glucose control, increased telomere length (longer life).

ALL these effects are seen in MEN, not women.
AND
Exercise has the SAME benefits.

Most science research studies are carried out on men and then generalised across the population. But, there are specific sex differences. Research specifically on women didn't show the same benefits as for men.

 How if affects women differently 
Kisspeptin (responsible for puberty/endocrine system and feedback for GnRH releasing hormone which is required for the menstrual cycle) is much more sensitive to disruption in women. Bascially, if you start restricting calories, within a few days you can start to fuck up your menstrual cycle.

Men's parasympathetic nervous system is switched on with fasting (lower heart rate, increased focus). In women it's the opposite. They become anxious, brain fog creeps in, increased heart rate.

There's no improvement in blood glucose control in women.

Autophagy is minimal in women. Massive for men.

It signals an increase in visceral fat storage for women. 

For health and for better body composition women are better off eating well in the day - FUEL YOUR EXERCISE (eat before/eat after) - and eat your dinner early evening. Don't snack and then you've done a fast from dinner to breakfast anyway. You need the calories in the day time and around your exercise. The longer a woman is in a catabolic state (breaking down state) the worse it is for her.