Fasting and Calorie Restriction


Fasting and Calorie Restriction

Therapeutic fasting and calorie restriction sound drastic, but research shows they may benefit a variety of conditions, including weight management and cancer.

Therapeutic fasting is probably one of the earliest therapies used in medicine. Calorie restriction is another type of therapy that practitioners prescribe.

Therapeutic fasting

Water fast for hypertension

One of the better known methods of therapeutic fasting (TF) involves the use of water-only fasting. In a study of 174 patients with high blood pressure (hypertension), a medically supervised water fast lasting approximately 10 to 11 days in a hospital setting resulted in 89 percent of individuals achieving complete normalization of their blood pressures.

Prior to the water-only fasting, medications were gradually discontinued. Patients consumed a vegan diet for two full days prior to the fast, and during the fast, physical activity was minimized while patients consumed a minimum of 40 oz (1.2 L) of distilled water daily.

The results showed substantial reductions in blood pressure, with the average drop being 37 systolic (the top number) and 12 diastolic (the bottom number). The outcome also suggested that these results could be sustained as long as individuals maintained a low-sodium vegan diet following the water-only fasting period.

Water fast for autoimmune diseases

In another report, six cases of patients with autoimmune diseases (lupus, multiple sclerosis, rheumatoid arthritis, and scleroderma) were studied for the long-term benefits of water-only fasting.

Patients were prescribed water-only fasting (at least 1 quart/950 mL a day) for periods of seven to 24 days while physical and mental activities were minimized. Prior to fasting, medications were gradually discontinued and all patients were placed on a vegan diet.

All patients experienced clinical remissions that were sustained as long as a vegan diet was adhered to following the fast. Some of the reasons for these improvements involved a “calming” of the immune system and the removal of toxins from fat and tissue stores.

Water fast for cancer

A small investigative study involved 10 patients who fasted for two to six days prior to chemotherapy and five to 56 hours following chemotherapy. Results clearly showed a marked reduction in major chemotherapy-associated side effects without compromising chemotherapy effectiveness.

While patients lost weight during the fasting periods, it was a non-issue since lost weight was easily regained when the patients consumed their regular diets. This preliminary report demonstrates that TF prior to and following chemotherapy appears to be an effective strategy for reducing the very difficult side effects that most patients experience.

Water fast for mood disorders

In a review of 92 studies involving TF and mood disorders, results showed that between the second and seventh day of fasting (either with only water or with 300 to 500 calories per day), patients experienced increased vigilance and mood improvement, a greater sense of well-being, and sometimes a feeling of euphoria.

Although it wasn’t clear why these improvements occurred, authors hypothesized they might involve the release of endorphins (the body’s own “feel-good” chemicals) or a decline in brain blood sugar resulting in nerve cell regeneration and improved neurotransmitter function. Another possibility is an increase in ketone bodies (a fasting-related process that causes fat to replace glucose as the brain’s major fuel source).

Therapeutic fasting has also been found to enhance mood among patients with rheumatic diseases and chronic pain syndromes. It’s not known if these favourable mood changes persist following TF.

Calorie restriction

Alternate-day calorie restriction

A reanalysis of a previously published study involved giving elderly patients a normal diet (around 2,300 calories) on one day, followed by a calorie restricted (CR) diet (about 900 calories) on alternate days. The study authors found corroboration for their hypothesis that alternate-day calorie restriction confers many health benefits.

The researchers who conducted this reanalysis also included their anecdotal experience with more than 500 subjects who, for a period of two and a half years, consumed an alternate-day CR diet (20 to 50 percent of the daily estimated caloric requirement).

They found the alternate-day CR diet to confer benefits within two weeks among subjects with conditions including insulin resistance, asthma, autoimmune disease, osteoarthritis, infectious diseases, cardiac arrhythmias, and menopausal hot flashes. They also suggested this pattern of eating might help in weight control by alleviating the difficulties dieters have when they deprive themselves of normal eating entirely.

Calorie restriction for weight management

In a six-month controlled clinical trial assessing the impact of CR among overweight (non-obese) patients, the results demonstrated statistically significant reductions in two biomarkers of longevity: the fasting insulin level and body temperature.

It is known that elevated fasting insulin levels are associated with diabetes, metabolic syndrome, and even cancer promotion. The authors speculated that these favourable reductions might confer antiaging benefits.

In another study of non-obese individuals, a CR diet plus exercise was found to improve insulin sensitivity, possibly the result of improved fat utilization.

In an extensive review of the literature pertaining to caloric and dietary restriction regimens, the overall findings were that CR, alternate-day fasting, or simply restricting a particular macronutrient, such as protein, all conferred health benefits.

  • CR showed improvement in overall health, cardiovascular health, and glucose regulation in humans.
  • Alternate-day fasting benefits involved mostly the cardiovascular system and glucose regulation.
  • Protein restriction appears to extend lifespan by around 20 percent, as a result of limiting the intake of the amino acid methionine.

What’s involved
Is it right for you?

One must first determine if such an undertaking is appropriate. A number of factors would eliminate therapeutic fasting or calorie restriction as a safe treatment. These include individuals with

  • an eating disorder
  • a body mass index below 20 or above 40
  • kidney or liver disease
  • a gastric ulcer
  • severe comorbidities, such as cancer (unless it is being used to reduce chemotherapy-related side effects)
  • alcoholism
  • pregnancy/lactation
  • unexplained weight loss
  • conditions requiring immunosuppressive (except corticosteroids) or diuretic medication

What comes next?

Assuming none of these contraindications exist, consult a health care practitioner experienced in TF before embarking on one of these treatments. Here are some of the steps you’ll be guided through:

  • Typically, medications are tapered prior to a TF, but some are also essential (thyroid and diabetes medication), so this would need to be discussed with the prescribing practitioner.
  • Once medications are tapered, a vegan diet is normally adopted seven to 10 days prior to fasting, consisting of raw fruits and vegetables, steamed vegetables, legumes, and fresh fruit/vegetable juices.
  • During the TF, which can last between one and three weeks, only distilled or spring water is consumed.
  • During the first few days of the fast, it is not uncommon to experience a worsening of physical or mental state, with a gradual marked improvement by about seven days.
  • It is paramount that activity be restricted during the TF since this helps to minimize issues relating to low blood pressure, arrhythmia, dehydration, and electrolyte disturbances.
  • Check in regularly with your health care practitioner during the fasting period so that your stability can be monitored.
  • Once the fasting period is over, it is followed by
    • one day of fresh fruit and vegetable juices (around 360 mL every three hours) if the fast was only one week
    • two days of juices if the fast was two weeks
    • three days of juices if the fast was three weeks
    • Then a vegan diet is reintroduced for several days, after which time the diet can be transitioned to a whole foods diet or one that is health promoting so the benefits of the TF can be maintained.

CR diets can vary with the individual. Some simply engage in their regular diet followed by a vegan diet on alternate days. Some individuals stop eating a particular food group, while some restrict their overall caloric intake by 200 to 600 calories daily. The key is to consistently adhere to the pattern.

Tips and precautions for a safe fast

  • Have the time and willpower to complete it. There is no point in undertaking a fast while on vacation or when your work/life demands are very high.
  • Discuss it with your health care practitioner so that a mutually agreed upon course of action can be developed, involving medication tapering and regular monitoring during the fast.
  • Try adopting a vegan diet long before the fast so that you understand what is involved.
  • Once the fast commences, be prepared to feel and experience different physical reactions and mental states. None should be of concern unless they are so profound that the fast must be stopped; otherwise they will pass usually within the first several days of the fast.
  • Limit all of your physical activity during the fast.
  • Don’t resume regular eating immediately following the fast.
  • Think of the fast as a time of introspection, learning, and perhaps regaining balance.


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