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| A thoughtful look at intermittent fasting: its history, weight-loss potential, risks, who should avoid it, and whether it fits different ages and bodies |
Yesterday, during a phone call, my son and his Dad talked about their current intermittent fasting experiences. I thought it was quite amazing that they were both choosing to do that, independent of having discussed it before. Their conversation echoed something many families are discovering at the same time: intermittent fasting has quietly become one of the most talked-about approaches to weight loss and metabolic health, without everyone necessarily agreeing on what it is, or whether it’s wise.
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What Is Intermittent Fasting and Where Did It Come From?
Despite sounding like a modern wellness trend, intermittent fasting (IF) is not new. Humans have fasted for religious, cultural, and practical reasons for thousands of years. What is new is the packaging of fasting as a structured, science-informed weight-loss strategy.
The modern IF movement began taking shape in the early 2000s:
Brad Pilon popularized short, intentional fasts with his book Eat Stop Eat (2007), suggesting one or two 24-hour fasts per week.
Martin Berkhan developed the Leangains approach around 2010, pairing a daily eating window (often 16:8) with strength training.
Dr. Michael Mosley, a British physician and science journalist, brought the 5:2 diet into the mainstream with his 2012 BBC documentary and later in his book, The Fast Diet.
Dr. Jason Fung, a Canadian nephrologist, framed intermittent fasting as a hormonal intervention rather than a calorie trick in The Obesity Code (2016), arguing that insulin regulation is central to fat loss.
Together, these voices shifted fasting from something people endured to something they chose.
Why Intermittent Fasting Appeals to So Many People
- One reason IF spreads organically—like it did between my son and his Dad—is its simplicity. There are no special foods to buy, no points to calculate, and no recipes you must follow.
- People often find IF attractive because:
- It limits eating opportunities, which can naturally reduce calorie intake without deliberate restriction.
- It simplifies decisions—fewer meals can mean less food noise.
- It may improve insulin sensitivity, helping the body access stored fat more easily.
- It fits many lifestyles, from busy professionals to retirees who no longer want to snack all evening.
- For some, it feels less like a “diet” and more like returning to an older rhythm of eating.
Does Intermittent Fasting Actually Work for Weight Loss?
Research suggests that intermittent fasting can support weight loss, but it is not magic.
Most studies show that IF performs about as well as traditional calorie-restricted diets when total calorie intake is similar. The advantage is not necessarily superior fat loss, but better adherence for certain personalities. If a person finds it easier not to eat at all for part of the day than to eat smaller portions all day long, IF can be effective.
However, fasting does not override poor food quality. Eating ultra-processed foods during the eating window still undermines results.
Basic “Rules” (and Variations) of Intermittent Fasting
There is no single IF plan, but common structures include:
- 12:12 – a gentle daily overnight fast (often considered a starting point)
- 14:10 or 16:8 – eating within a daily window
- 5:2 – two very low-calorie days per week
- 24-hour fasts once or twice weekly
Most approaches emphasize:
- Water, black coffee, or plain tea during fasting
- Protein-adequate meals
- Avoiding binge-eating to “compensate” for fasting hours
Does the Fasting Window Have to Be the Same Every Day?
Research suggests that consistency helps, especially for blood sugar regulation and circadian rhythm alignment. That said, modest shifts, especially with a 12-hour fast, still appear beneficial. More extreme or erratic schedules may increase stress hormones in some people, particularly women.
Who Should NOT Do Intermittent Fasting
Intermittent fasting is not appropriate for everyone. It should be avoided or medically supervised for:
- People with a history of eating disorders
- Those with diabetes on insulin or sulfonylureas
- Pregnant or breastfeeding women
- Individuals with low body weight or nutrient deficiencies
- People who experience dizziness, anxiety, or sleep disruption while fasting
For these groups, fasting can be destabilizing rather than healing.
Potential Risks and Unhealthy Patterns
While IF is often presented as “natural,” it can become problematic when:
- Fasting turns into chronic under-eating
- It masks disordered eating under a wellness label
- It elevates cortisol, especially with poor sleep or excessive exercise
- Social isolation increases because meals are avoided rather than enjoyed
Fasting is a tool, not a virtue.
Is There a Gender or Age Component?
This is where debate becomes livelier.
Some clinicians, including Dr. Mindy Pelz, argue that women, especially post-menopausal women, need more cautious, hormone-aware fasting protocols. Others, like Dr. Jason Fung, maintain that women benefit similarly to men when fasting is done gently and consistently.
Research suggests that women may be more sensitive to prolonged fasting, particularly when calorie intake becomes too low or stress is high. Many experts recommend shorter fasting windows (12–14 hours) for women, especially later in life.
Who Supports IF—and Who Pushes Back?
Supportive voices include:
- Jason Fung
- Michael Mosley
- Mark Sisson
- Rhonda Patrick (with nuance)
More cautious or neutral voices include:
- Marion Nestle
- Harvard Health clinicians
- Many registered dietitians who emphasize sustainability over structure
The loudest critics tend to focus less on fasting itself and more on how it is sometimes oversold.
Summing Up:
Intermittent fasting is neither a miracle nor a menace. For some, it restores balance and clarity around eating. For others, it creates stress, rigidity, or harm. Its growing popularity may say less about fasting itself and more about a collective desire to eat with intention again, without constant grazing or guilt.
Like many health practices, its wisdom lies not in the rulebook, but in how gently and honestly it is applied.
🥤 Article and photos © 2025 Cynthia Zirkwitz | Organic Granny
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