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
. Choose 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 ,
Foodie Under 200 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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Plateau / Losing & regaining same few lb: Many folk have a plateau after losing 15 lb +, while their body rebalances.
It may also be a longterm "set point" weight, so homeostasis is causing your body to resist losing more fat.
Just be patient & you'll break through.
However, if this persists for 4 weeks+ then typically you are overeating on NFDs, so aim to average within TDEE - mfp for a week, to reality check.
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Lots to lose - how to speed up weight loss
Optionally calculate the lower TDEE for goal weight, but eat to current weight TDEE at least 1 day per week.
This helps your body adjust to needing less food as you lose weight.
Also trains you how to eat to maintain goal weight.
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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
5:2/IF Exercise Thread #3 gives advice & support on combining 5:2 with exercise.
The OP explains science behind fasting, exercise & health & has many calculators.
Recipe Thread has many FD recipes. Post your own too.
Inspirational Thread has reports from Mumsnet 5:2ers who have lost weight.
Scientific Evidence for Fasting & Health
BBC article on the original 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.
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.
He compared 5:2 to ordinary daily diets on overweight women with family history of breast cancer.
Fasting group lost more belly fat, retained more muscle & had slightly better blood sugar regulation.
More of his research is in HealthyAging , Health , AvoidParkinsonsDisease
His article in J Aging Mech Disease 2015 explains the health benefits of intermittent fasting in great scientific detail.
Why intermittent fasting and stopping snacking can lower your risk of serious diseases:
Meal frequency and timing in health and disease
This interview with leading researchers into fasting in combination with standard cancer treatment: ScientificDiscussion MoselyMattsonLongo and a LongoInterview
NY Times Fasting Overview
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.
Any lurkers and newbies, come join us and share your experiences too. These are lovely supportive threads and everyone is welcome !