Long-term caloric restriction is known to provide a variety of health benefits. But it can be difficult for people to stay compliant with caloric restriction. In a recent review articlescientists analyzed the scientific literature and found that intermittent fasting provides the same benefits of caloric restriction. Intermittent fasting is defined as a period of fasting of at least 12 hours, during which the body flips a “metabolic switch.” When this switch is triggered, the body shifts from the use of glucose/carbohydrate for energy to the use of ketones from lipid/fat. The flipping of this switch triggers a state called ketosis.

There are a variety of ways to achieve ketosis with intermittent fasting. One popular method is time-restricted feeding, in which all the calories for the day are consumed within a limited window of 6 to 8 hours. Another method is alternate-day fasting, in which the individual eats normally for one day, and then eats 0to 500 calories the next day, alternating between the two.

The benefits of intermittent fasting-stimulated ketosis outlined in the review include:

  • Loss of body fat, with the preservation of muscle (this is unlike traditional weight-loss approaches, in which muscle mass is usually lost)
  • Improved glucose metabolism (decreased insulin resistance)
  • Reduced inflammation
  • Reduced blood pressure, both systolic and diastolic (improved hypertension)
  • Improved cardiovascular health (decreased triglycerides and total and LDL cholesterol)
  • Improved tolerance of stress and disease
  • Overall improvement of metabolic syndrome
  • Decreased risk of cardiovascular disease and type 2 diabetes
  • Improvement of cognitive function
  • Greater improvement of endurance as a result of strength training

It’s worth noting that most of these effects have been shown only for overweight or obese subjects, and some only in animal models. The body of research on this topic is not complete. An average of 5 kg (11 lb) was lost in the clinical trials that showed benefits of intermittent fasting, so weight loss may be an important component of the therapeutic benefit. The duration of the successful studies was at least eight weeks long, so intermittent fasting should be followed for a minimum of two months before expecting significant benefit.

Obtaining medical advice is recommended before beginning an intermittent fasting regimen, especially for individuals with a medical diagnosis and/or on medications. Ideally, intermittent fasting should be combined with strength training, and foods consumed during the feeding window should be in line with a healthy ancestral diet. Once an intermittent fasting routine is initiated, it is important to ensure that the switch has been flipped (and thus ketosis has been achieved). A trained nutrition professional can make the process easier and safer. They can also help select the best intermittent fasting protocol, specific diet, and means of measuring ketosis for each individual.