Fasting Diets

Fasting Diets

Fasting diets have been lingering around as fad diet trend for some time now. Nutrition advice floating around the internet about fasting diets has been based largely on limited scientific research done mostly on animals and anecdotal evidence. However, there is some human research in the beginning stages indicating there might be some truth to the diet claims surrounding fasting. Calorie restriction has been the focus of a growing body of metabolic and aging research, and fasting is one way to achieve calorie restriction in an effort to improve metabolic health and age-related diseases. There are various protocols of fasting including intermittent fasting and periodic fasting.

Claims about fasting include:

  • Boosts metabolism for increased fat loss
  • Increases insulin sensitivity
  • Lengthens lifespan
  • Protects against neurodegenerative diseases
  • Reduces oxidative stress
  • Reduces risk of heart disease
  • Reduces blood pressure and cholesterol levels

Basic Types of Fasting

Intermittent fasting is a daily fasting pattern with set eating and fasting windows. This limits your feeding window to 12 or less hours a day. One of the common splits is 16 hours fasting and 8 hours eating. It is suggested that men respond best to a 16 hour fast and 8 hour eating split; for women, a 14 hour fast and 10 hour eating window. Traditional intermittent fasting protocol involves fasting through the night and breaking the fast in the early afternoon hours.

Periodic fasting is a full day fast done once a week, month or year. It is recommend that you don’t fast for more than 24 hours once a week. Current research indicates that 4 to 5 days of fasting can have health benefits lasting for up to several months. However, most of this research however is done on rats and primates.

Emerging Fasting Research

Prolonged period fasting research done in primates that share 93% of the human genome has shown that calorie restriction extends the lifespan significantly. Calorie restriction without malnutrition had a positive impact on primates survival. Another similar study showed no significant change in lifespan, but the caloric content given to this group of monkeys was lower. This could indicate that adequate calories to avoid malnutrition play a crucial role in the outcomes of following a fasting diet.

Research done in rats has shown an increase in lifespan up to 40%. With such an increase, it would be expected to see an increase in disease biomarkers, but this is not the case. This study actually found reduced instances and decreased risk factors for cancer, diabetes and cardiovascular disease. One interesting effect of this eating pattern was a decrease in organ size; when normal eating resumed the organ systems returned to normal size.

Scientists have identified growth factor IGF-1 as as an important mediator, but the biology of exactly how this pathway works with the effects on aging and extending lifespan is still not totally understood and not without risk.

The Possible Negatives

  • Most of the research to date has been done using animal models on mostly rats and some primates. Human data is extremely limited.
  • Intermittent fast research is often compared with the typical American suboptimal hypercaloric diet full of highly processed macronutrients, chemical additives, and environmental pollutants. So most research cannot prove that health benefits are from intermittent fasting versus diet composition.
  • Finding your sweet spot for an appropriate feeding and fasting window is very dependent on your activity level making it challenging to make sure you are actually doing more good than harm- like muscle protein breakdown.

Should I Try Fasting Eating Patterns?

Based on the current evidence, it is very likely that simply eating less calories than you burn that are comprised of real foods like fruits, vegetables, whole grains and lean proteins is just as beneficial as intermittent fasting protocols. Prolong periodic fasting and fasting mimicking diets are looking excitingly promising but still just in the beginning stages of understanding how this complex biology works. A healthy eating plan paired with exercise might just be all you need. The key to making lasting change for success with nutrition is picking what works for your lifestyle.

People that should definitely avoid fasting eating patterns:

  • Pregnant women
  • People with eating disorders or recovering from eating disorders
  • Individuals with health conditions that require other medical nutrition therapy approaches

Practical Applications

If you decide to try intermittent or periodic fasting, here are a few things to keep in mind:

  • Your feeding window isn’t a free-for-all. Make sure to adhere to a nutrient dense diet including lean proteins, fruits, vegetables and whole grains if you want to see the benefits.
  • Take it easy on the processed foods. This applies to anyone and everyone, not just the fasting crazed crowd.
  • Working out fasted can have negative effects on muscle mass. Intermittent fasting protocol has your workout falling right before your first meal. I do not recommend this. But if you are going to do it, have 10 grams of branched chain amino acids (BCAAs) to mitigate muscle loss.


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