Impact of intermittent fasting on the body weight of overweight and obese individuals

The efficacy of intermittent fasting (IF) on weight loss and metabolic parameters compared to continued caloric restriction is controversial. Although it has gained many followers among patients, literature is still conflicting due to some unclear aspects. First, there are different definitions of what is considered IF. Most studies started observing the effects of religious fastings, such as Ramadan. Later, other protocols emerged mostly investigating the 5:2 diet, characterized by two days a week considered as “fasting” days, and alternate-day energy restriction, alternating between days considered as “fast” or “feed”.¹ Other protocols with time-restricted eating, typically adopting 16h fasting and 8h eating, has also being applied with varied results.² Due to the different approaches regarding IF, it is difficult to compare studies and discuss possible benefits.

Secondly, still considering methodological aspects, studies on IF usually include a small number of subjects, have short-term interventions, and often lack an appropriate control group, such as continued caloric restriction. This is evident in the systematic review by Lima et al.³, which, after a criterion approach, resulted in the inclusion of four studies. In overweight or obese subjects, most interventions that somehow promote caloric restriction or increased expenditure tend to result in short-term weight loss. Adherence to IF for longer periods should be evaluated, especially when transposing clinical studies to a free-living setting. Nevertheless, the adoption of IF has shown some benefits on weight loss and control of some metabolic parameters, such as glycemic control and parameters related to cardiovascular diseases.⁴,⁵

Finally, an important aspect that should be mentioned when considering IF is related to practical issues. Obesity is a multifactorial disease that is not caused solely by a misbalance between calories consumed and spent; it evolves hormonal and behavioral mechanisms. Individuals do not eat only to suppress physiological hunger. There are important cultural, social, and economic aspects influencing food choices and eating behavior. There is no clear evidence that adopting IF could be a trigger for eating disorders but the presence of disordered eating behaviors should be considered by health professionals when deciding whether or not IF could be an option for weight loss strategy.⁶

REFERENCES

• ¹
  Harris L, Hamilton S, Azevedo LB, Olajide J, De Brún C, Waller G, et al. Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis. JBI Database Syst Rev Implement Rep. 2018;16(2):507-47.
• ²
  Malinowski B, Zalewska K, Węsierska A, Sokołowska MM, Socha M, Liczner G, et al. Intermittent fasting in cardiovascular disorders: an overview. Nutrients. 2019;11(3). pii: E673.
• ³
  Lima CR, Oliveira IK, Frota K, Carvalho C, Paiva AA, Campelo V, et al. Impacto do jejum intermitente no peso corporal em indivíduos com sobrepeso e obesidade. Rev Assoc Med Bras. 2020; 66(2): 222-226.
• ⁴
  Stockman MC, Thomas D, Burke J, Apovian CM. Intermittent fasting: is the wait worth the weight? Curr Obes Rep. 2018;7(2):172-85.
• ⁵
  Patterson RE, Sears DD. Metabolic effects of intermittent fasting. Annu Rev Nutr. 2017;37:371-93.
• ⁶
  Schaumberg K, Anderson DA, Reilly EE, Anderson LM. Does short-term fasting promote pathological eating patterns? Eat Behav. 2015;19:168-72.

Publication Dates

• Publication in this collection
  04 May 2020
• Date of issue
  Feb 2020