Welcome to the continuing thread for those following 5:2 or other forms of IF (Intermittent Fasting) such as 4:3, ADF, or daily 16:8 
The 5:2 diet was introduced by Michael Mosely 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 roughly the number of calories your body needs to maintain - NOT reduce - its weight (see TDEE calculator below).
IMPORTANT
If you have had Eating Disorders you should NOT do 5:2 or any other kind of fasting
ACRONYMS
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, this 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
BMI (Body Mass Index) healthy range is 18.5 - 24.9 for Caucasians. Upper limit may be 22 for some of Asian origin.
FD = Fast Day: aim for 500 calories (600 for men or 25% TDEE if higher) or 1000 cals for BF
Even if you exercise strenuously, do NOT increase FD cals
MFP = My Fitness Pal, a useful App or website to track food & drink calories
NFD = Non-Fast Day, averages around TDEE
NSV / LSV = Non Scale Victory / LifeStyle (change) Victory, e.g. compliment, smaller waist, new skinny jeans
SV = Scale Victory
TDEE = Total Daily Energy Expenditure, the average number of calories you burn in a day, is calculated (see calculators below) from your current weight, height, age, activity level.
Aim to average about this for NFDs.
WOE / WOL = Way Of Eating / Way Of Life. We say this instead of "diet", to emphasise that we must make a permanent change in how we eat, to mainitain our new healthy weight longterm.
HOW TO START
. Take initial measurements: weight, waist, hips
. Use TDEE calculator below as a rough guide to how much to eat on NFDs
. Chokose any 2 days for FDs, non-consecutive is easier.
. Before each FD: plan, shop & calorie count ALL food & drink for the day
Useful Resources & Calculators
Calorie Counter: mfp , mfp
Calories for NFD: TDEE Calc
FD Recipes: BBC Good Food 52 , Mosely LowCarb ,
Good2Know , Vegetarian
NHS 10 Recipes under 100 cals , Mirror 5:2 50 snacks under 50 cals
Any Day: Meal Planner
FD Ready Meals, Takeaways, Restaurant: Mirror , Indie
Safe Alcohol: Calc Daily UnitsCalories , Calc Weekly Units
BMI: Calc
Body Frame Size: Calc
Calc Ideal Weight Range
Body Fat: Calc
Choose / Visualise Goal Weight: 3D BMI body variations ripped to normal , Bod Vis Measurements & 3D rotate
FAQs / Tips
- WATER: Start each day with a glass of water; and drink plenty during the day.
- HOT DRINKS: No limits on tea or coffee, but on FDs count any milk / sugar calories.
- 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 less than you burn. 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
Instead, calculate NFD target with your activity level set one level below what you estimate.
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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.
Most prefer either to skip breakfast & save most cals for supper, or have 2 meals.
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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.
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NFDs: No rules, but to improve health, try to cut down on added sugar & junk food, keep alcohol within safe limits. A few treats per week are fine.
Aim for TDEE, but you may under-eat by say 20% on 3 NFDs to save calories for weekend.
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To speed up 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.
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Do NOT fast: if you've ever had EDs, or if pregnant, under 21, over-stressed, fever, stomach bug, 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, alcohol.
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CHECK with your Doctor: if you have diabetes, any other endocrine condition, any serious past or present medical condition, or if taking ANY prescribed medication (fasting may affect absorption rate)
Useful MN Threads
Exercise: BigChocFrenzy gives advice & support on combining 5:2 with exercise. The OP explains the science behind fasting, exercise & health and has many calculators.
Tips and Links : BreadandWine collects practical tips & info gained over all the 5:2 threads.
Inspirational EatRiskier has reports from Mumsnet 5:2ers who have lost weight.
Recipes: FrenchFancy has many FD recipes. Post your own here too.
Maintaining: talkinpeace's thread is for those who have successfully lost weight on 5:2/IF and are now maintaining (some for over 3 years )
Scientific Evidence for Fasting & Health
BBC article on the Horizon program
Telegraph comments on 5:2 and gives a brief overview by Dr Mosley, useful for newbies.
This InterviewPart1 and InterviewPart2 with leading ADF researcher Dr Varady explains why fasting helps you to lose weight AND improves some health markers.
A science Study specifically addressed the effect of this diet on obese men & women, wrt health and 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, - in most diets, 25% of lost weight is muscle, up to 50% for sleb crash diets.
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%)."
Dr Michelle Harvie (funded by cancer charities) showed possible benefits of intermittent fasting compared to standard daily calorie reduction in her trials (consecutive FDs) with women at high risk of breast cancer: ComparingDiets , EarlierResearch52
Dr Johnson showed intermittent fasting helped Asthma
Why Intermittent Fasting Works: Mattson , BlackSwan and Hormesis
Molecular Mechanisms and Clinical Applications: J CellMetabolism
Recent research into the health benefits of fasting: e.g. by world-respected neuroscientist Dr MarkMattson showed:
. Improved glucose regulation
. Loss of abdominal fat with maintenance of muscle mass
. Reduced blood pressure and heart rate
. Improved learning and memory and motor function
. Protection of neurons in the brain against dysfunction and degeneration in animal models of Alzheimer’s disease, Parkinson’s disease, stroke and Huntington’s disease.
Some of his research is in HealthyAging , Health , AvoidParkinsonsDisease
His recent article in J Aging Mech Disease 2015 explains the health benefits of intermittent fasting in great scientific detail.
Also this interview with a leading researcher into fasting in combination with standard cancer treatment: ScientificDiscussion MoselyMattsonLongo and a LongoInterview
Research by other US and European scientists in this DailyTelegraph Article about the medicinal uses of fasting, for many serious conditions & diseases.
Recent trials with Type 2 diabetics and those at risk of having it used a form of daily fasting - skipping supper.
Their conclusions: eating 1-2 meals per day is better than several small meals for losing weight and controlling insulin levels, see Type2Paper
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 !