Scottsdale Weightloss Center

Yes! Intermittent Fasting Works


Periods of very-low-calorie intake force our bodies to burn fat to meet our energy needs. When fat burns, it releases ketones that cause the body to make less ghrelin, a hunger hormone. As a result, intermittent fasting can increase metabolism, decrease hunger, and increase fat burning. Here’s why intermittent fasting works and how we use it in our medical weight loss program.

Intermittent Fasting and Medical Weight Loss

Intermittent fasting (IF) is a new and exciting method for weight loss medicine. Like all diets, IF is most successful when combined with the support of a medical specialist.

For example, if Monday is a fasting day then you don’t eat from Sunday dinner until breakfast on Tuesday. In that timeframe, you only consume 600 calories of prescribed medical meal replacements. You’d consume a 200 calorie shake for breakfast, lunch, and dinner. Each protein shake provides a third of your daily nutrition. By working with an expert medical provider, you’ll receive 100% of your daily nutrition on only 600 calories.

The following day is non-fasting. It usually consists of a low-calorie, low-carbohydrate meal plan of 1000-1200 calories. We limit carbohydrates on non-fasting days to prevent your metabolism from shifting from fat burning to sugar burning. That’s why it’s helpful to work with a medical provider while fasting. We can even adjust medications for high blood pressure or diabetes during IF.

What to Expect While Intermittent Fasting

In our weight loss program, the first day of intermittent fasting is the most difficult part of the process. But we can assure you, it does get easier with time. While fasting, your body uses up stored sugar in the liver and muscles. The feeling of hunger lasts until your bodies use up the last sugar storage, then you might “hit the wall.”

During your first week of intermittent fasting, you may feel a bit sluggish or have a headache. This usually lasts for 1/2 a day. To help these feelings pass, we encourage increased salt intake (pickles or soup bullion) and drinking lots of fluids. Once this feeling passes, the headache usually passes and energy improves. Many patients tell us they have no hunger and notice an improvement in feelings of well-being after the first fast. These feelings often persist during weight loss.

Who Benefits from Intermittent Fasting

There is no single diet that works best for everyone. Many of our weight loss program patients do best on a continuous low-calorie diet. Some do best on a low-carbohydrate meal plan.

For most people, intermittent fasting results in the same weight loss as a low-calorie diet. As experts in obesity medicine, we can predict the best and safest approach based on one’s medical history and past diet results. With meal plans, education, and medications, you’ll experience the most dramatic weight loss with intermittent fasting.

Types of Intermittent Fasting

Alternate Day (5:2) Fasting

Dr. Michael Mosely personally used alternate day fasting that lead to a weight loss of 20 lbs and a complete reversal of his diabetes. He ate 500 calories twice per week and ate a limited intake for the other five days. This regimen is now called 5:2 intermittent fasting. Further studies have shown that alternate day fasting (ADF) was as effective as low-calorie diets, improving cholesterol and insulin levels.

Time-Restricted Feeding

Time-restricted feeding (TRF) involves consistent fasting and eating within a 24-hour cycle. This form of fasting means you skip breakfast every morning and push the first meal of the day to lunch, eating all your calories in an 8-hour window. It can lead to moderate weight loss and increase metabolism, but further studies are needed. In our experience, the 5:2 36-hour intermittent fast offers better promise than TRF.

The Longest Fast on Record

In 1965, at 456 pounds, Angus Barbieri set the world record for the longest fast. He fasted for 382 days, consuming only tea, coffee, carbonated water, electrolytes, and vitamins. Barbieri lost 276 lbs, reaching his goal weight of 180 lbs. Undertaking a fast of so extreme is dangerous without close medical supervision. That’s why Barbieri was monitored closely by physicians.

types of intermittent fasting for weight loss

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NEJM 381;26 Dec 26, 2019. Effects of Intermittent Fasting on Health, Aging and Disease by Rafael de Cabo Ph.D. and Mark P. Mattson Ph.D.

Longo VD and Mattson MP. Fasting: Molecular Mechanisms and Clinical Applications. Cell Metabolism. 2014;19(2):181-192.

Varady KA, Hellerstein MK. Alternate-day fasting and chronic disease prevention: a review of human and animal trials. Am J Clin Nutr. 2007;86:7–13.

Halberg N, Henriksen M, Soderhamn N, et al. Effect of intermittent fasting and refeeding on insulin action in healthy men. J Appl Physiol. 2005;99:2128–2136.

Lihn AS, Pederson SB, Richelsen B. Adiponection: action, regulation and association to insulin sensitivity. Obes Rev. 2005;Feb 6(1):13-21.

Heilbronn LK, Smith SR, Martin CK, Anton SD, Ravussin E. Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism. Am J Clin Nutr. 2005;81:69–73.

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