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Intermittent Fasting 101

by | May 1, 2020 | FAST FACTS, FAST START | 0 comments

While there are several different types of intermittent fasts, one of the more popular approaches to IF is known as the 5:2 diet in which individuals significantly cuts back their calorie intake to no more than 500-600 calories a day, twice a week, on non-consecutive days. For the other 5 days of the week, it’s eating as usual. Other IF diets include complete fasts during which no food is consumed for a specific length of time (commonly 16-24 hours), also twice per week.

No matter which specific IF plan is followed, the results can be impressive for those seeking to optimize their health, lose weight, and lower their body fat percentage. Here are some of the most common benefits of periodically implementing an IF plan into your diet…

IF Can be a Highly Potent Tool for Weight Loss

Losing excess weight is the primary reason people consider some type of IF plan(1). By reducing the number of meals consumed, IF frequently leads to an automatic reduction in calorie intake, resulting in greater weight loss.

Another way IF facilitates weight loss is by eliciting a change in hormone levels. Due to hormonal changes, short-term fasting may significantly increase your resting metabolic rate(2). In addition, the changes in hormone levels allow for stored body fat to be more accessible for needed energy when food is not available.

By taking in fewer calories and burning more calories, IF delivers the ultimate, one-two weight loss punch by adjusting both sides of the calorie equation.

Scientific studies continue to support the efficacy of IF for the purpose of greater weight loss. In one study, IF proved to be a highly effective component in the reduction of body fat and body weight for obese women. The study also supported the added benefit of IF lowering the risk of coronary heart disease among this same population.

In another study of the effects of IF on body composition, the restricted eating approach demonstrated impressive weight loss results over 12 to 24 weeks(4). Here, participants were able to reduce body weight by 3% to 9% during this time period. Compared to a majority of weight loss studies, these numbers demonstrate significantly greater results.

These successful weight loss results were achieved both by limiting meals during the week and by avoiding binging or taking in excess calories during eating periods. It’s a simple formula, but one that must be strictly adhered to for optimal weight loss and fat loss results.

Additional Health Benefits of IF

When implemented correctly, IF can be a powerful and effective tool for losing weight and body fat. Moreover, there are additional health advantages when it comes to this eating approach. In studies performed on animals and humans, IF boosted body and brain functioning and increased longevity.

For instance, inflammation – a primary cause of various chronic diseases – can be significantly reduced by following an IF eating plan(5,6).

IF has also been shown to help prevent certain types of cancer, and it plays a significant role in delaying or holding back tumor growth. According to several studies(7), findings suggest that multiple cycles of fasting are effective in delaying the progression of different types of tumors and could potentially replace or augment the efficacy of certain chemotherapy drugs in the treatment of various cancers.

Heart health is another area where IF has proven to be beneficial in reducing the major risk factors of heart disease – LDL cholesterol, blood sugar, inflammation, and insulin resistance(3,8).

Supporting a sharp mind is just as important as a sound body, and here again IF has demonstrated positive effects on brain health. IF can increase a brain hormone called BDNF and can contribute to the development of newly generated neural cells; in turn, the chances of neurodegenerative disorders are reduced. IF appears to lead to greater brain functioning and less likelihood of suffering from dementia or Alzheimer’s disease(9,10).

The health outcomes of IF also translate to anti-aging benefits and greater longevity. According to several key studies performed on mice and rats, IF was shown to lengthen the lifespan of the rodents by as much as 83%(11).

Whatever health issue is your primary concern, the physical and mental benefits brought about by IF are many. Science has shown adhering to IF in a measured and systematic approach can help you feel, think, perform, and live better.

It should be noted, however, that IF research is still in its infancy. Further scientific exploration of IF is necessary to more fully determine the impact of IF on humans. Some findings suggest IF is not suited for all populations such as pregnant woman, underweight individuals, and elderly persons who have increased nutritional demands.

Common Pitfalls & Side Effects

Here are some of the more common pitfalls and adverse side effects that can arise through intermittent fasting…

Hunger is the main side effect of IF, especially for those who are new to this type of eating pattern. Along with complaints of being hungry during IF, these same people may admit to feeling tired and weak. Even though these challenges may be temporary until the body and mind can adapt to the change in diet, some people call it quits before any health and weight loss benefits can be experienced.

Another common pitfall of IF is succumbing to binge eating during non-fasting days; binging can counteract any intended health and weight loss goals. By eating uncontrollably on non-fasting days, IF eating plan participants can counter any progress made during their fasting periods and can trigger weight gain and spikes in blood sugar. “It’s human nature for people to want to reward themselves after doing very hard work, such as exercise or fasting for a long period of time, so there is a danger of indulging in unhealthy dietary habits on non-fasting days,” says Dr. Frank Hu, Chair of the Department of Nutrition at the Harvard T.H. Chan School of Public Health.

Similarly, stopping the fast altogether can also lead to weight gain, as many people return to old eating habits rather than modifying their diet to maintain any progress they achieved through IF. Although often temporary or short-term, other physical side-effects of IF can include heartburn, headaches, and diarrhea. Lastly, those with a history of eating disorders or other medical conditions must consult with a doctor prior to beginning an IF regimen.

One way to avoid these pitfalls is to try a different type fast, like a Fasting Mimicking Diet or Time Restricted Eating.

For those who have the green light and desire to move forward, IF can offer a host of mental and physical benefits. Combined with ample exercise, sleep, and good nutrition, IF can be one of the most effective ways to lose weight and improve overall health and well-being.


  3. Klempel, M, Kroeger, C, Surabhi, B, Trepanowski, J, & Varady, K 2012, ‘Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women’, Nutrition Journal, 11, pp. 98-117, Academic Search Elite, EBSCOhost, viewed 30 April 2018.
  5. Faris “, Kacimi S, Salem M, et al. Intermittent fasting during Ramadan attenuates proinflammatory cytokines and immune cells in healthy subjects. Nutrition Research [serial online]. December 2012;32(12):947-955. Available from: Academic Search Elite, Ipswich, MA. Accessed April 30, 2018.
  6. Johnson J, Summer W, Mattson M, et al. Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology & Medicine [serial online]. March 2007;42(5):665-674. Available from: Academic Search Elite, Ipswich, MA. Accessed April 30, 2018.
  9. Mattson M. ENERGY INTAKE, MEAL FREQUENCY, AND HEALTH: A Neurobiological Perspective. Annual Review Of Nutrition [serial online]. August 2005;25(1):237-260. Available from: Academic Search Elite, Ipswich, MA. Accessed April 30, 2018.
  11. Goodrick C, Ingram D, Reynolds M, Freeman J, Cider N. Effects of intermittent feeding upon growth, activity, and lifespan in rats allowed voluntary exercise. Experimental Aging Research [serial online]. Fal 1983 1983;9(3):203-209. Available from: PsycINFO, Ipswich, MA. Accessed April 30, 2018.

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