Intermittent Fasting - Specialist Nutrition Rehab


21 Sep 2021

Intermittent Fasting


Intermittent fasting (IF), is an umbrella term used to describe various regimes where someone voluntarily restricts or abstains from food and calorie-containing beverages for a set period of time.  The three most popular regimes of IF include:

  • Alternate-day fasting – where people alternate between days consuming 0-25% of their calorie requirements, and days with unrestricted eating.
  • Time-restricted feeding – where people consume all of their calories within a set time-frame (eg. between 7am to 3pm) and then fast for the remaining hours (eg. 16 hours).  The most common ratio is to eat within an 6-8 hour window, and fast for 16-18 hours.
  • Modified-fasting regime (also called whole day fasting) – where people consume only 20-25% of their calorie requirements (~500-600kcal) on scheduled “fasting” days, but then eat as desired on the other days per week.  The most common example of this is the 5:2 diet, where people restrict their food intake on 2 non-consecutive days per week, and then eat without restriction on the other days.

There are numerous health claims associated with IF, from improved cognitive function to weight loss to increased longevity, but the majority of research to date has been done on animals.

Of the research done on humans, the weight loss and metabolic benefits associated with IF (eg. blood pressure, plasma lipids, inflammatory markers) are equivalent to what is produced by general calorie restriction.1,2,3

Considering that 55-67% of clients with a brain injury, and 66% of clients with a spinal cord injury, have a Body Mass Index (BMI) which puts them in the overweight to obese categories, is intermittent fasting something these clients should consider as a weight loss strategy?4,5

Who should try it…and who shouldn’t?

IF is not appropriate for everyone.  People who take insulin for their diabetes, those who are prone to hypoglycaemia, people with a history of disordered eating or an eating disorder, people who need to take medication with food, pregnant women and breastfeeding women should not try IF.1  Medication adjustments may also be required, so the GP will need to be notified prior to someone starting IF.  For example, people on thyroid medication may need to adjust the dose and timing of their medication.6

In the absence of the above health conditions, here is what clients will need to weigh up, to decide if IF is right for them:


  • IF can result in weight loss.  Weight loss (whether from IF or general calorie restriction) can result in improvements in blood pressure, blood glucose and cholesterol levels.
  • Some people feel that IF is easier to implement than daily calorie restriction.  Clients who do well with following “rules,” may prefer this type of eating and it may help them lose weight.
  • It can help someone regain interest and enthusiasm in losing weight, especially if they have hit a plateau or are just bored with their current regime.
  • Some of the newer research suggests that the benefits of IF may be greater when eating times are set for earlier in the day (to better match circadian rhythms).2


  • There is a higher risk of clients not meeting their requirements for vitamins, minerals and protein.  This is a significant risk, considering 0% of clients are meeting their nutrient requirements after a brain injury, even when eating times are not restricted.7
  • Protein intake needs to be distributed throughout the day for maximum muscle-building benefit.  There is a risk with IF that a client won’t consume enough protein, or the protein they do eat won’t be used as effectively, if their window for eating is more limited.8,9
  • Hunger may negatively affect fatigue levels, concentration and mood.  Alternate-day fasting has been found to have the highest drop-out rates, due to the intense hunger people experience on low-calorie days.2 Modified fasting has the highest compliance rate.1
  • If IF eating times are set for the late evening, this can interfere with sleep and cause blood glucose levels to increase.2
  •  Gastrointestinal symptoms, such as wind, bloating and constipation can be triggered by alternating between fasting and non-fasting states.1
  • IF won’t be effective if people consume excess calories on their non-fasting days.


As with most things in rehab, the skill is knowing which technique to use with which client at which time.  Clients who have been discharged from hospital following a major trauma and who want to try IF, should do so under the supervision of a dietitian.  A dietitian can ensure IF is done safely, without compromising  nutritional status and in a way that doesn’t interfere with other rehab goals.  Of course not everyone needs a formal IF regime.  Anyone can just offset a few days of overindulging with a few “lighter” days of eating.

For more information or to make a referral to a dietitian, please contact us at or 0121 384 7087.

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Specialist Nutrition Rehab
West Midlands
B24 0PL


07787 603 863

0121 384 7087

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