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July 13, 2023
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A look at intermittent fasting: A potential strategy for patients with obesity

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In the quest for practical strategies for treating obesity, intermittent fasting has emerged as a popular and potentially transformative approach.

Intermittent fasting is still one of the hottest fads, although it has been around in popular literature since at least 2016 with Dr. Jason Fung’s book The Obesity Code.

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In 2020, nearly one-quarter of Americans reported having tried intermittent fasting, making it the most popular nutrition plan trend. Although the most common interpretation of intermittent fasting involves fasting for 16 hours and eating for 8 hours in a 24-hour period (the 16:8 protocol), some would argue that this constitutes more of a time-restricted feeding pattern rather than true fasting.

Common intermittent fasting patterns include:

  • Daily time-restricted feeding: This is most often a 16-hour overnight fast from 8 p.m. until noon, although the specific hours one chooses to fast may not affect efficacy. Otherwise known as skipping breakfast. All meals would be eaten between noon and 8 p.m.
  • The one meal a day (OMAD) plan: OMAD can be done every day or can be used as part of a 5:2 plan. It would typically mean fasting from dinner one night until dinner the next, with only noncaloric beverages during the day.
  • The 5:2 plan: On the 5:2 plan, one would fast 2 days a week and eat normally for 5. On fasting days, one might employ either a 16:8 protocol or an OMAD plan.

Benefits of intermittent fasting for dieters include reported improvements in hunger once the body acclimates to the fasting protocol. Most of the weight loss benefit of fasting comes from the calorie restriction that it provides; however, other health benefits include improvements in insulin sensitivity, blood pressure, inflammation, stress response and sleep.

Intermittent fasting does come with some risks, especially for people with insulin-dependent diabetes and children. However, even these subgroups can use fasting safely if they follow the guidance of their health care provider. Most people can safely fast for 10 hours, which would mean not eating between 8 p.m. and 6 a.m. — the hours most people usually sleep. Other risks are more prevalent in those using the OMAD plan, which potentially puts them at risk for developing sarcopenia from not taking in enough protein. Health care providers should caution patients to stay well hydrated during their fasting hours. They should warn against prolonged fasting, which can increase the risk for cardiac dysrhythmias, gout, kidney stones and postural hypotension.

Intermittent fasting is one more tool in the clinician’s toolkit for treating patients with obesity. It can be especially useful for individuals who hate to cook or are not in the habit of planning regular meals because it reduces decision fatigue. For shift workers, it can help to organize meals into a consistent time frame, even though the sleep and wake cycles may be disrupted from day to day. For those practicing intermittent fasting on an inconsistent schedule, it may help to think of calorie goals weekly rather than daily. Some days, when the patient is not fasting, they may not be in a deep calorie deficit; however, when the fasting days are averaged into the weekly total, the patient can carve out a deeper deficit. This should result in more efficient weight loss.

It is important to note that intermittent fasting alone does not guarantee that the patient will be in a calorie deficit or that they will achieve weight loss. The quality of the food they eat during their eating window still matters. It is even more important to ensure that patients meet their protein requirements. A protein-forward approach to meal planning aims for a minimum of 30 g of protein at each meal when eating three normal meals. If the patient is eating only two meals, the goal is 50 g of protein per meal. This will ensure that muscle protein synthesis is being triggered, which will protect against the risk for sarcopenia by repairing, maintaining and building muscle.

Intermittent fasting is an advanced skill. I recommend starting patients on intermittent fasting only if they are already fasting or asking about it. Because most patients I see are not getting adequate protein when they come to me, my first step is to increase protein intake. Once they have gotten comfortable eating more protein and effectively reducing their carbohydrate intake, intermittent fasting can be introduced more safely to get them into a more significant calorie deficit. Fasting is suitable only for some. I screen my patients for a history of disordered eating, especially anorexia nervosa. For those patients, fasting may trigger unhealthy patterns of over-restriction.

Intermittent fasting offers a promising approach to combat obesity and promote weight loss. However, it is essential to remember that intermittent fasting may not suit everyone. Clinicians should work to meet the individual needs of each patient to develop a personalized obesity treatment plan that includes nutrition and lifestyle changes.

The 2022 Clinical Practice Statement on Nutrition and Physical Activity by the Obesity Medicine Association would be a valuable starting place for a clinician interested in using intermittent fasting with patients.

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