Welcome to the continuing thread for those following 5:2 or other forms of Intermittent Fasting such as 4:3, ADF, or daily 16:8
The 5:2 diet was introduced on BBC Horizon on August 2012:
Basically it is 2 very low cal days ("fasts") per week - which need not be consecutive - and eat "normally" the other 5 days.
For those who have dieted or maybe overeaten for years, eating "normally" means somewhere around the number of calories your body needs to maintain - NOT reduce - its weight ( see TDEE calculator below).
For most folk, 5:2 results in a weekly 3000 calorie deficit, so averages 1 lb loss. However, some folk may lose much more quickly / slowly or in fits & starts.
Initial weight loss may be much quicker.
If you have a lot of weight to lose, you may lose much more quickly than someone in the healthy BMI range who just wants to trim a few lb.
Acronyms & Calculators:
16:8 is a different type of fasting, which can be combined with 5:2.
Daily zero-cal fast for 16 hours and eat within an 8 hour window. To lose weight normally needs a weekly calorie deficit as well
4:3 = fast on 3 non-consecutive days per week
ADF (Alternate-Day Fasting) = fast every other day
FD = Fast Day: aim for 500 calories (600 for men) or 1000 cals for BF
If you exercise, do NOT increase FD cals
MFP = My Fitness Pal, a useful website or app to track food & drink caloriesi
NFD = Non-Fast Day, averages around TDEE
NSV / LSV = Non Scale Victory / LifeStyle (change) Victory, e.g. compliment, smaller waist, new skinny jeans
TDEE = Total Daily Energy Expenditure, the average number of calories you burn in a day. TDEE is calculated from your current weight, height, age, activity level.
Aim to average about this over the week's NFDs.
To speed up your weight loss and to train yourself how to eat on maintenance,
optionally calculate the lower TDEE for goal weight,
but eat to current weight TDEE at least 1 day per week.
WOE / WOL = Way Of Eating / Way Of Life. We say this instead of "diet", to emphasise that to maintain our new healthy weight longterm requires a permanent change in how we eat.
How to Start
. Take initial measurements: weight, waist, hips
. Use TDEE calculator above as a rough guide to how much to eat on NFDs
. Choose any 2 days for FDs
. Before each FD: plan, shop & calorie count ALL food & drink for the day
Useful MN Threads
Browse previous threads in the fasting section
Tips and Links : breadandwine’s thread collects practical tips and info we have gained over all the 5:2 threads. It is especially useful for newbies.
Inspirational: eatriskier’s Thread has reports from Mumsnet 5:2ers who have lost weight.
Read to boost your motivation.
Add your own when you have lost weight too 
Recipes: frenchfancy has collected delicious FD recipes from all the threads.
Post your own here too.
Exercise: bigchocfrenzy has a Thread for advice & support on combining 5:2 with a healthy exercise regime.
The OP explains the science behind fasting, exercise & health and has many calculators.
Maintaining: talkinpeace has a Thread for those who have successfully lost weight on 5:2/IF and are now maintaining.
Some of those sharing experiences have been maintaining for 2 years, which shows 5:2 is sustainable longterm.
Other Links
BBC article on the Horizon program
Telegraph comments on 5:2 and gives a brief overview by Dr Mosley, useful for newbies.
This health blog Interview with a leading scientist gives some of the scientific explanation for why fasting helps you to lose weight AND maybe improve your health too.
A science Study specifically addressed the effect of this diet on obese people (men & women), wrt health amd weight loss:
"... After 8 weeks of treatment, participants had an average 12.5 lbs reduction in body weight and a 4cm decrease in waist circumference. Total fat mass declined by about 12 lbs while lean body mass remained relatively constant."
i.e. almost all the weight lost was fat, not muscle or water, which is unusually good for a diet.
It also describes improved blood values:
"Plasma adiponectin, a protein hormone that is elevated in obesity and associated with heart disease, dropped by 30%. As did LDL cholesterol (25%) and triglycerides (32%)."
More for hard-core science geeks: Mattson , BlackSwan and Hormesis
If you’ve been researching IF you may have come across [[http://www.paleoforwomen.com/
shattering-the-myth-of-fasting-for-women-a-review-of-female-specific-responses-to-fasting-in-the-literature/ this article]] which is very negative about fasting for women with normal BMI.
Here’s our response:
- With a healthy BMI, those who want to be leaner will usually find weight and waist loss to be much slower than for overweight folk, since less fat and inches are available to lose.
- The women with healthy BMIs already had healthier blood sugar than the men in the study. Hence nothing really needed improving.
- Women who have had health problems on IF were NOT doing 5:2, but the
much tougher ADF or 16:8, combined with heavy lifting (often multiples of body weight) like LeanGains
AND
were often starting from already ultra-low BF 12-16% range.^
-Many were already missing periods or had EDs before IF, due to the low BF %, over-training and over-stressing.
5:2 is a gentler form of IF than ADF or Leangains and there’s plenty of anecdotal evidence from longterm 5:2ers, now with healthy BMI, who are continuing to have very positive results and experiences on this WOE.
These Pictures illustrate that many different body shapes & types that are healthy, so there is no single "right" shape.
FAQs / Tips:
- WATER: Start each day with a pint of water; and drink plenty during the day.
- HOT DRINKS: No limits on tea or coffee, just count any milk / sugar calories on FDs.
- FDs: If possible, choose days when you are busy, but not preparing meals for others.Concentrate on protein & veg; avoid / reduce starchy carbs & sugar, including juice.
Soups & stews are good; ready meals are fine.
Many prefer to skip breakfast & save most cals for supper.
- BFers: start with 1000-cal FDs; optionally, reduce to 700 cals gradually. You can return to 1000 if growth spurts or sleep-deprivation require more fuel.
- NFDs: No rules, but to improve health, try to cut down on added sugar and junk food. A few treats per week are good though!
Aim for TDEE, but you may under-eat by say 20% on 3 NFDs to save calories for weekend.
- CLENCH for health: Men & women should exercise pelvic floor daily
- SLEEP: Try to get enough sleep, or it may slow weight loss.
- EXERCISE: is healthy & can help weight loss - BUT only if you do NOT eat back exercise calories. Fasted training can burn more fat.
HIIT and resistance training both work well with 5:2/IF.
If you exercise, do NOT increase FD cals
- Do NOT fast: if pregnant, under 21, over-stressed, have EDs, fever, even a bad cold.
When ill, your body usually needs more nutrients and less stress. So don't force yourself to eat, but if hungry then eat nutritious food to TDEE & cut out junk, added sugar, fizzy drinks.
- CHECK with your Doctor: if you have diabetes, any other endocrine condition, or if taking ANY prescribed medication (fasting may affect absorption rate)
Roundup
A BIG THANK YOU to everyone who has contributed their experience and tips over all these threads.
This has created a wealth of very valuable practical knowledge to help us all.
Any lurkers and newbies, come join us and share your experiences too. These are lovely supportive threads and everyone is welcome !
) so I'm hoping if I can lose another 3lb before I start my new job in 2 weeks they might look ok. 
. I need my sleep to Bimble.
, but fending it off with lots of cups of tea. Lunchtime can't come soon enough.