Intermittent fasting refers to eating patterns that cycle between periods of eating and periods of fasting (or greatly reduced intake). Common examples include time-restricted eating (e.g., 16 hours fasting / 8 hours eating), alternate day fasting, or 5:2 style (very low calories two days per week). From a clinical viewpoint, the appeal is that beyond “just eat less,” IF offers a structured pattern which may simplify decision-making, improve adherence, and potentially yield benefits in weight and metabolic health. As dietitians, we view it as worthy of a viable option in our toolbox as other "eating patterns" like Paleo, Whole 30, Mediterranean diets-- but IF must be tailored, monitored, and integrated with foundational nutrition principles rather than replacing them. If you’re considering it, we can walk through which approach might suit you, how to implement it safely, and how to measure progress.

What does the research show?

Here are some key findings:

• A systematic review and meta-analysis of randomized controlled trials found that fasting strategies (among 623 participants) led to slightly greater short-term weight loss (≈0.9 kg more) and fat-mass reduction (≈1.08 kg) compared with continuous caloric restriction. Also improved insulin sensitivity.

• Another meta-analysis in adults with metabolic syndrome (6 RCTs) showed that IF significantly reduced BMI (mean difference −1.56 kg/m²), fat mass (−1.35 %), waist circumference (−3.06 cm), and HOMA-IR (−0.62) vs non-fasting controls. 

• A newer meta-analysis (8 RCTs, 573 participants) indicates IF reduced fasting blood glucose (WMD ≈ −3.34 mg/dL), HbA1c (WMD ≈ −0.08 %), LDL-cholesterol (≈ −6.42 mg/dL) and IL-6 (a marker of inflammation). 

• Large network meta-analysis of 99 RCTs (6,582 adults) found that while all IF and continuous energy restriction (CER) reduced weight relative to no intervention, alternate-day fasting yielded a modest advantage (~1.3 kg more weight loss) compared with CER.

• In people with insulin-treated type 2 diabetes, a 12-week RCT (“INTERFAST-2”) showed that 3 non-consecutive days of IF per week significantly reduced HbA1c (~7.3 mmol/mol) and allowed insulin dose reduction vs control. 

Our stance — individualize, individualize, individualize

Given the evidence, here’s how we interpret IF (if one chooses to) in practice:

• IF appears to be a viable tool for weight loss and improving insulin sensitivity, similar to traditional caloric restriction but only in populations where prolonged fasting isn't harmful to health, mental wellbeing or one's relationship with food.

• The structured time window may help clients who struggle with constant food decisions or late-night eating, this might be a great option however, long-term success on this eating pattern is contingent upon consistently adhering to it. If one stops IF, the health outcomes may change. 

• For certain metabolic conditions (e.g., pre-diabetes, type 2 diabetes) emerging evidence supports safety under supervision (though more long-term data are needed) this translates to a person adhering to medical appointments, routine blood sugar monitoring and a flexible approach to how IF looks and feels individually. 

Why caution is needed

• The benefits, while statistically significant, are modest in many cases — e.g., ~1 kg advantage over CER or small HbA1c changes. IF is not a magic bullet.

• Long-term data (beyond 6–12 months) are still limited. Sustaining a fasting pattern may be challenging for some people.

• Fasting may not be appropriate (or requires modification) for certain populations: pregnant or breastfeeding women, children/adolescents, people with a history of disordered eating, or some chronic illnesses.

• The quality of foods consumed during the “eating window” matters a great deal — IF does not override the fundamentals of nutrient-dense eating.

• Some recent observational data raise concerns around overly strict fasting windows (e.g., <8 h eating window) and cardiovascular outcomes; though causality is not established, it reinforces the need for individualized and moderate approaches.

Bottom line, an eating pattern that is appropriate for one person is appropriate for one person. There are no "one-size-fits-all" nutrition approaches for all adults or kids. Bring up your interest in IF with your care team if you'd like to try it and ask questions such as: "Is IF right for me? Why or why not?" "I'm interested in IF for (fill in the blank reason you are interested in it) what are your thoughts about this?" "How much does diet influence my health conditions and what pattern of eating is ideal in your opinion?" You are the best advocate for your health!