Is Fasting Better Than Calorie Reduction for Long-Term Weight Loss?

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Both fasting-based strategies (FBS) and continuous caloric restriction (CCR) effectively promote weight loss and improve metabolic health in obese adults, although fasting may offer slightly better short-term results in weight and fat reduction.

However, the differences between the two are not clinically significant, and both methods show similar long-term outcomes. FBS notably enhances insulin sensitivity, but more research is needed to determine its long-term benefits.

FBS protocol is defined as a period of eating and fasting periods, while CCR is based on consistently reduced daily calorie intake, generally 20% to 40%, without altering the timing or frequency of meals. FBS is lauded for its simplicity and benefits in terms of weight loss and metabolic health. Intermittent fasting, alternate-day fasting and time-restricted eating are all examples of this method.

CCR had been a strategy of weight management programs for years, with previous research supporting its efficacy. However, challenges with CCR include adherence and continued caloric reduction can lead to feelings of hunger and deprivation, which ultimately lead to relapse.

While both strategies aim to create a calorie deficit, research is still uncertain as to which is more effective for both long- and short-term weight loss, as well as metabolic outcomes.

“The effectiveness of FBS compared to CCR is still a subject of debate, with conflicting findings from various studies,” wrote a team of Spanish investigators. “This systematic review and meta-analysis aims to address the gaps in current research by comparing the effectiveness of FBS and CCR in terms of weight loss, body composition, and metabolic outcomes in obese adults. By synthesizing data from RCTs, this review seeks to provide a clearer understanding of whether FBS offers any distinct advantages over CCR for short- and long-term weight management.”

In this review and meta-analysis, investigators compared both strategies on these parameters in obese adults. Ten randomized controlled trials comprised of 623 subjects were included for comparison.

Ultimately, both interventions led to weight loss among participants, with a reduction of 5.5 to 6.5 kg observed at six months. Although the FBS group had slightly greater short-term reductions in both fat mass and body weight when compared with the CCR group, these differences were not clinically significant. Additionally, both strategies had comparable effects on lean mass, waist and hip circumference, lipid profiles, blood pressure and glucose metabolism.

Patients following a FBS plan had improved insulin sensitivity and significant reductions in fasting insulin and homeostatic model assessment of insulin resistance (HOMA-IR).

Investigators noted limitations including the heterogeneity among patients receiving fasting interventions, such as treatment durations. Sensitivity analyses and random effects models were applied and performed to account for these potential sources. Additionally, many of the trials were short-term interventions that lasted less than six months, which hindered the insights into long-term effects of fasting strategies on weight loss and metabolic outcomes.

These interventions did not consistently control dietary intake, which could have impacted results. Lastly, these trials recruited a homogenous cohort of patients with obesity who did not report metabolic or psychological comorbidities. As such, findings should be interpreted with caution prior to being applied to populations that are more vulnerable to these specific conditions.

“Despite the short-term benefits, fasting strategies did not demonstrate superior long-term outcomes compared to CCR,” investigators emphasized. “Therefore, both methods appear equally effective for weight management, and further research is needed to explore the long-term clinical implications of fasting interventions in obese individuals.”