Anti-Aging Health Weight Loss

Achieve the Best Intermittent Fasting Results

By Kim Crawford, M.D. Last updated: September 6, 2018
intermittent fasting results

How To Practice Intermittent Fasting

If you want to learn how to achieve the best intermittent fasting results, then you must consider the various types of fasting. The different intermittent fasting schedules include time restricted feeding (TRF), true intermittent fasting (IF), different caloric intakes for fasting and fasting mimicry (which is relatively new). To help you decide which is best for you, I’ll explain how to practice each type of fasting and reveal the drawbacks and benefits.

Alternate Day Fasting

Following this type of diet plan is straightforward; fast every other day. Liberal water is advised. There is no restriction to eating on the “eating days.”

Alternate Day Partial Fasting, Intermittent

intermittent fasting resultsStudies have been performed on people instructed to cut calories by 25% of “normal” intake on two non-consecutive days of the week. Eating is “normal” on non-calorically-restricted days.

Intermittent Fasting 5:2 Diet Plan

This plan is a well-known diet kick-off plan. It is called the 5:2 diet because on two non-consecutive weekdays (usually Monday and Thursday), there is a set calorie count given for men and women, regardless of size or metabolism. Men are asked to consume 600 calories, with women consuming 500 calories. There is no restriction to food intake on the other five days.

Time Restricted Feeding

This type of eating has been touted as a way to benefit health while controlling weight; with the moniker “intermittent fasting 16:8” being the most popular iteration of this way of eating. Eating is done within a specified time frame. For example, individuals eat within an eight hour period during the day, resulting in a 16 hr fast. This has been popularized by the “Bulletproof” fasting method, where ketosis is induced in the morning via a “fatty” cup of coffee, and then food is ingested from 2 to 8 PM.

However, the studies have all been done with complete fasting during the “fasting time.” There is no doubt that nutritional ketosis is beneficial for detoxification (specifically autophagy) and brain health. To point out, we don’t have specific studies which look at whether or not ketosis is mimicking the effects of fasting. It might be; we’re just not sure.

Prolonged fasting

Short term prolonged fasting is considered to be three days or less where either juice or bone broth only are consumed. The “prolonged” version of this fast is to perform it for up to 30 days.

Religious fasting

During Ramadan, for example, there is a period where people will fast from sunrise to sunset. Seventh Day Adventists practice time restricted feeding.

Fasting Mimicking Diet (FMD)

I would be remiss if I did not mention this “commercially-based” version of practicing intermittent fasting. It involves severe caloric restriction for five consecutive days of the month. It was developed by Dr. Valter Longo, University Southern California Longevity Institute of Longevity. It uses kits containing 770‐1100 calorie plant‐based nutrients. Even more important, its development and positive results have been documented for over a decade.

Resveratrol Ingestion

Resveratrol supplementation has many benefits. To clarify, no, you certainly cannot get the amount you need from drinking wine, as many people believe. Resveratrol is anti-cancer, part of a TNF-alpha drug mimicking regimen for autoimmune disease, and mimics fasting, too.

Summation of Scientific Studies on Intermittent Fasting Results

Weight and Metabolic control

We see improvement in fat oxidation and a decrease in oxidative stress. Further, insulin sensitivity improves, blood pressure goes down, and there is an improvement in the metabolic efficiency of the GI microbiome. Autophagy (a form of detoxification) is also enhanced. Indeed, all of this results in a big boost to weight loss and weight control programs.

Intermittent fasting variants also stimulate the production of human growth hormone. Low levels of HGH result in increased body fat, lower lean body mass, and osteopenia (bone thinning). HGH converts into IGF‐1 (insulin-like growth factor‐1) in the liver. Improving HGH levels improves lean muscle and bone mass. As an example of the effects, studies show a five-fold increase in HGH in response to two days of fasting.

Cardiac Improvements

Heart rate variability is improved; meaning your heart responds better to stress. As mentioned, blood pressure goes down, and inflammatory markers do as well. HDL increases and triglycerides decrease; both linked to reducing coronary artery disease.

Brain health

Intermittent fasting is great for your brain. Studies show subjects with mild cognitive impairment experience an improvement in cognition. This is the result of several mechanisms. There appears to be a brain-protective effect with improved neuronal resistance to injury as well as a decrease in neurodegeneration. Significantly, studies show a demonstrable boost in brain-derived-neurotrophic factor (BDNF), which is responsible for many brain-healthy effects. In addition, it supports brain neuroplasticity (the formation of new neurons and neuronal connections), improves brain signaling, and even helps with weight by decreasing appetite and improving glucose metabolism.

Miscellaneous Benefits

Fasting programs are cancer-protective and help to prevent and control autoimmune disease. They also enhance mitochondrial biogenesis.  As a point of fact, not practicality, prolonged fasting stresses the body more and produces more profound results. Longevity, as measured by telomere length, is also improved by all types of fasting.

Intermittent Fasting Potential Downsides

We cannot confirm the effects of intermittent fasting on the hunger hormones; meaning leptin and ghrelin with the potential for rebound hunger. Due to this issue, I often recommend to patients who have hunger or cravings, either a good dopamine boost with l-tyrosine and SAMe and/or ketosis during fasting; using keto-adapted lifestyle changes and MCT oil or a good ketone supplement. Whereas some studies hint that fasting may improve one’s mood, we cannot confirm it’s effect on either mood or stress hormones.

Most patients I treat require adrenal support; some require mood support. Studies performed on athletes reveal that intermittent fasting (but not time restricted feeding) may impact the athlete’s ability for more intense exercise. However, other studies of IF (not TRF) reveal bouts of hypoglycemia in both athletes and non-athletes. Further, some studies show alternate day and 5:2 plans are not effective for either weight loss or positive health changes when people consume too many calories on non-fasting days.

Not only that but also plans where a 25% reduction in calories is required show (on average) that study subjects were only able to cut down by 12%. Animal studies show a decrease in fertility; so fasting would not be recommended during times of desired fertility, pregnancy, or breastfeeding. Finally, the last potential downside is that IF is a lifestyle, and this must be done on an ongoing basis for sustained results. The proponents of the fasting mimicking diets argue that taking the calorie count down just five days per month, with all foods in a “kit” might be a more natural lifestyle practice.

What is the Best Intermittent Fasting Schedule?

After reviewing the literature, trying all fasting first hand and having patients try various IF programs, I can conclude the following universal findings. Water-fasting for a whole day is hard if you are not in ketosis. If you’re trying to work, it’s hard to concentrate, and you’re hungry all day. If you do it for three days, by day three you’re headed into ketosis, so that day is easier. But, in all honesty, fasting is just “painful” and the only time I insist on a “real fast” is to improve operative results in someone having surgery, or to improve the results of a reduced-dose-chemotherapy session for a patient with cancer. Even then, I often will allow for a ketotic-state-fast.

It’s quite difficult to be on the 5:2 schedule for a long period. However, if someone chooses that method, I have them drink alternating water and antioxidant-powdered drinks all day and a high protein filling meal (like scrambled eggs and broccoli) for dinner. This is a good weight-loss kick-off diet, but it’s just not sustainable for life. After examining the contents of the five-day monthly eating plan that is popular in some medical circles, I conclude that while some people will find this to be “easy,” others will not be happy with their eating choices; and no matter what, this will overlap with weekdays and weekends. The eating plan that will allow for a normal work-day and exercise sessions and sustainable hunger pangs appears to be IF 16:8.

Intermittent Fasting 16:8 (or 18:6)

This is time restricted feeding; I recommend becoming keto-adapted (meaning you can switch in and out of ketosis at will) before you adopt this lifestyle. Here’s your plan:

  1. Morning: Have black coffee. You can probably add a little stevia and a splash of additive-free coconut milk. You can put MCT oil in your coffee if you want, but I take MCT or a ketone supplement separately; so as not to wreck a perfectly good cup of coffee. “Bulletproof” coffee is likely okay as well which is coffee, blended with MCT oil and grass-fed butter; we don’t know if a beverage will duplicate the study results, but I predict “yes.”
  2. Afternoon: Have a healthy lunch at noon (for the 16:8 plan) or 2 PM (for the 18:6 plan). To quell post-meal hunger pangs and get the benefits of continued ketosis, make this a keto-meal.
  3. Evening: Have dinner at 7 PM (adjusted to which plan you are on); Note: Do not consume food or beverages three hours before you go to bed. You can break ketosis, but don’t go so overboard that it’s hard to get back into ketosis the next morning.
  4. From the time you finish dinner to the time you eat your next real meal, you will fast for 16 or 18 hours.

Both ketosis and fasting are great for your metabolism, weight management, and brain health. For these reasons, I recommend this variant as the “life eating plan” and follow the 16:8 on weekdays and the 18:6 on weekends (with the fasting being in ketosis) myself. Bon appetit!

Selected References
 2018 Feb;16(2):507-547. doi: 10.11124/JBISRIR-2016-003248.

Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis.

Harris L, Hamilton S, Azevedo LB, Olajide J, De Brún C, Waller G, Whittaker V, Sharp T, Lean M, Hankey C, Ells L.
 2017 Dec 5;26(6):884-896.e5. doi: 10.1016/j.cmet.2017.09.024. Epub 2017 Oct 26.

Dietary Restriction and AMPK Increase Lifespan via Mitochondrial Network and Peroxisome Remodeling.

Weir HJ, Yao P, Huynh FK, Escoubas CC, Goncalves RL, Burkewitz K, Laboy R, Hirschey MD, Mair WB.
PMID: 29117546

Intermittent Fasting Promotes White Adipose Browning and Decreases Obesity by Shaping the Gut Microbiota

Guolin Li, Cen Xie, Siyu Lu, Robert G. Nichols, Yuan Tian, Licen Li, Daxeshkumar Patel, Yinyan Ma, Chad N. Brocker, Tingting Yan, Kristopher W. Krausz, Rong Xiang, Oksana Gavrilova, Andrew D. Patterson, and Frank Gonzalez  
 2017 Aug 21;37:371-393. doi: 10.1146/annurev-nutr-071816-064634. Epub 2017 Jul 17.

Metabolic Effects of Intermittent Fasting.

Patterson RE, Sears DD.
. 2017; 2017: 3932491.

Impact of Time-Restricted Feeding and Dawn-to-Sunset-Fasting on Circadian Rhythm, Obesity, Metabolic Syndrome, and Nonalcoholic Fatty Liver Disease

Ayse L. Mindikoglu, Antone Opekun, Sood K. Gagan, and Sridevi Devaraj 
 2017 Jun 15;595(12):3691-3700. doi: 10.1113/JP273094. Epub 2017 Apr 25.

Timerestricted feeding for prevention and treatment of cardiometabolic disorders.

Melkani GC, Panda S.
. 2017 Mar; 9(3): 222.
 Matching Meals to Body Clocks—Impact on Weight and Glucose Metabolism
Amy T. Hutchison, Gary A. Wittert, and Leonie K. Heilbronn
 2017 Mar;17(2):200-207. doi: 10.1080/17461391.2016.1223173. Epub 2016 Aug 22.

Timerestricted feeding in young men performing resistance training: A randomized controlled trial.

Tinsley GM, Forsse JS, Butler NK, Paoli A, Bane AA, La Bounty PM, Morgan GB, Grandjean PW.
References to Fasting Mimicry:

Brandhorst et al., A Periodic Diet that Mimics Fasting Promotes Multi‐System Regeneration, Enhanced Cognitive
Performance, and Healthspan, Cell Metabolism (2015),
Longo V, Cortellino S., Enhancing Stem Cell Transplantation with “Nutri‐Technology.”

Cell Stem Cell 2016: 19;6, 681‐682.
Choi et al., A Diet Mimicking Fasting Promotes Regeneration and Reduces Autoimmunity and Multiple Sclerosis Symptoms, Cell
Reports (2016),

Martinez‐Lopez N, et al. Autophagy and Aging. Adv Exp Med Biol. 2015;847:73‐87.
Jung CH, et al. mTOR regulation of autophagy. FEBS Lett. 2010;584(7):1287‐95.

Wei M, et al. Fasting‐mimicking diet and markers/risk factors for aging,
diabetes, cancer and cardiovascular disease. Sci Trans Med. .2017;1‐12.

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