Fasting diets now occupy a perch near the top of a growing pile of weight-control plans.

Washington State University researchers say that “intermittent fasting” was the most frequently searched diet term online last year.

And intermittent fasting was the second most popular plan among the 38% of adults who claimed to follow any weight-control diet.

Intermittent fasting apps, books, blogs, and articles seem to be everywhere, and clinical evidence of its weight and metabolic benefits continues to grow.

Before we delve into new evidence for the benefits of fasting diets, let’s quickly review the major types.

Fasting comes in varied forms
Continuous fasting simply means that you cut your daily calorie intake by as much as one-quarter but don’t change your eating patterns or vary your calorie intake from day to day.

Intermittent fasting plans vary — these are probably the most popular:

  • 5:2 diet: Eat as usual five days of the week but cut calories drastically on the other two days.
  • Alternate-day fasting: Consume your normal calorie needs — or a bit more — one day, then consume many fewer calories the next day, and repeat that alternating pattern.
  • Time-restricted eating: Compress daily food consumption into short periods and — optionally — eat smaller portions to cut your total daily calorie intake. You might for example skip breakfast and dinner and eat only during the middle of the day.

You’ll find more about fasting — and some relevant clinical research — in Fasting Diets Gain Fans and Credibility and Does Sporadic Fasting Win for Health & Weight?.

Now, let’s look at the results of two small clinical studies that provided more encouraging evidence that intermittent fasting helps with weight and cardiometabolic health — even to the point where patients could drop their diabetes drugs.

Canadian clinical study affirms anti-diabetic power of fasting
Jason Fung, M.D., is a kidney specialist at Canada’s University of Toronto and one of the leading researchers in intermittent fasting.

Dr. Fung and a group of Canadian and Caribbean-based medical colleagues conducted a small study involving three patients with diabetes (Furmli S et al 2019).

All three patients were asked to follow a so-called “therapeutic fasting” diet for 12 weeks, which meant abstaining from all calorie-containing food and drinks during a specified period.

The precise fasting schedules varied, depending primarily on the patient’s preference, and ranged from going 16 hours to several days without calories.

The patients were encouraged to favor low-carbohydrate meals and foods, and to take a multivitamin supplement to ensure adequate nutrition. They could down any amount of very-low-calorie drinks such as water, coffee, tea, and bone broth.

On fasting days, the patients ate only dinner, while they ate lunch and dinner on non‑fasting days. To limit their blood glucose and insulin levels, the patients were encouraged to largely avoid sugar and refined carbohydrates on days when they ate any foods.

After 12 weeks, all three participants had lost weight and reported feeling fine throughout the study.

Better yet, their diabetes prescriptions became entirely or largely unnecessary for all three patients within a few weeks of starting their fasting regimens: two were able to stop taking all their diabetes drugs, while the third was able to stop taking three out of four of their prescribed drugs.

California clinical study sees weight, blood pressure, and vascular benefits
Last month, a California-based team — led by University of California San Diego scientists — published the encouraging results of their NIH‑funded study (Wilkinson MJ et al. 2020).

They recruited 19 participants who’d been diagnosed with metabolic syndrome, most of whom were taking a statin drug and/or blood pressure drug(s).

Metabolic syndrome (MetS) raises the risk of developing diabetes and/or heart disease, and the U.S. NIH defines MetS as having any three or more of these characteristics:

  • High blood pressure — 130/85 mm Hg or higher
  • High blood triglyceride level — 150 mg/dL (1.7 mmol/L), or higher
  • High fasting blood sugar level — 100 mg/dL (5.6 mmol/L) or higher
  • Large waist — 35 inches (89 cm) or more for women and 40 inches (102 cm) or more for men
  • Low levels of “good” HDL cholesterol — Less than 40 mg/dL (1.04 mmol/L) in men or less than 50 mg/dL (1.3 mmol/L) in women.

Before the study began, the participants reported typically eating food during a window of 14 hours a day or a bit longer.

For this 12-week study, the volunteers ate only during 10 hours of “time-restricted feeding” or TRE — in other words, they chose a daily 10-hour window during which they consumed all their food.

By the end of the three-month study, all 19 patients displayed signs of better cardiovascular and metabolic health, such as losing weight, shrinking their waste, and lowering their cholesterol and blood pressure levels.

As the authors wrote, “TRE [time-restricted eating] is a potentially powerful lifestyle intervention that can be added to standard medical practice to treat metabolic syndrome.”

Based on this encouraging outcome, which needs confirming, the California team plans to conduct a larger study involving at least 100 people with metabolic syndrome.



  • Furmli S, Elmasry R, Ramos M, Fung J. Therapeutic use of intermittent fasting for people with type 2 diabetes as an alternative to insulin. BMJ Case Rep. 2018 Oct 9;2018. pii: bcr-2017-221854. doi: 10.1136/bcr-2017-221854
  • Melkani GC, Panda S. Time-restricted feeding for prevention and treatment of cardiometabolic disorders. J Physiol. 2017 Jun 15;595(12):3691-3700. doi: 10.1113/JP273094. Epub 2017 Apr 25. Review.
  • Wilkinson MJ, Manoogian ENC, Zadourian A, Lo H, Fakhouri S, Shoghi A, Wang X, Fleischer JG, Navlakha S, Panda S, Taub PR. Ten-Hour Time-Restricted Eating Reduces Weight, Blood Pressure, and Atherogenic Lipids in Patients with Metabolic Syndrome. Cell Metab. 2020 Jan 7;31(1):92-104.e5. doi: 10.1016/j.cmet.2019.11.004. Epub 2019 Dec 5.