R52 refers to Reverse 5:2 Intermittent Fasting.
An R52 approach requires that you eat to your maximum calorie count two (2) non-constitutive days per week and fast the other five (5) days.
On fasting days you have two major restrictions.
- Maximum number of calories allowed is 10% of your max
- Your Glycemic Load cannot exceed 11 units for the day
So for example, if on non-fasting days you are allowed 2400 calories, then on fasting days you cannot have more than 240 calories from all sources.
There are a few other recommendations that will improve your success
- No products containing Aspartame or similar sugar substitutes (Stevia is okay)
- No products containing more than 1g of sugar per serving
- No Wheat or Gluten products
- No products with a Glycemic Index above 50
- No Dairy
You do not need to adjust your daily routine, however it is recommended that you do some form of aerobic exercise for a minimum of 1 hour spread throughout the day. Most smart phones include a step counter so 6000-7000 steps per day should be sufficient.
On non-fasting days you have two major restrictions
- You must eat at least your maximum calorie allowance
- You must not eat more than 1.25x this allowance
So for example, if on non-fasting days you are allowed 2400 calories then you should eat between 2400-3000 calories on those days. It is important not to go below your maximum calorie count because what we are trying to do on these days is let your body know it should not be decreasing its metabolism to offset the lower calorie counts on the fasting days.
There are no restrictions on the types of food you can eat on these days however, these recommendations will improve your success
- Focus on real whole foods, not processed foods
- Cook at home rather than eat out
- Stay away from products claiming to be ‘diet’ or ‘low-calorie’
- Use nutrition plans and recipes based on either Keto or Mediterranean food preparation guides
- Limit sugars and sugar ladened products
You should continue to do your walking or other exercise. In addition, add some form of anaerobic exercise to your daily routine for 15-20 minutes throughout the day and after meals. The idea here is to build up endurance, not build muscle. Use light weights and multiple repetitions (20-40) rather than heavier weights trying to ‘lift to failure‘.
While two times per week isn’t a lot, what you are doing here is breaking down some muscle and using the extra protein as part of your non-fasting days to rebuild and strengthen which will help with energy usage on your fasting days.
Everyone has days where their routine gets broken for various reason. Birthdays, holidays, friends get-together, etc.. If you need to break your routine for any reason simply get back into a fasting cycle at the first opportunity and fast for a minimum of 3 days after to get back on track.
Extending the Fasting Days
Current research seems to suggest that the most beneficial results from fasting that occur between 4 and 10 days in length. Longer duration fasts have not been studied effectively to determine the positive or negative impacts. A number of studies have looked at long term intermittent fasting (< 400 cals/day) verses long term very low calorie deficiencies (i.e. between 800 and 1200 cals/day) and seem to suggest that there is no statistical difference. Notwithstanding, there is a measurable drop in resting metabolism with VLCD diets that has a permanent impact on metabolism which doesn’t happen with fasting.
As a result, this guide is currently recommending that if you extend your fasting, that you limit to at most 10-14 days and have your blood work checked by your doctor every 2-3 months.