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| - Last Updated on December 3, 2024 by Dr Priyamvada
Quick Take
A social media post claims that fasting for 17 hours kills cancer cells. We did the fact check to term this claim as mostly false.
The Claim
According to a post on X, “After 13 hours of fasting, men’s testosterone levels go up, which can improve sex drive, muscle strength, and brain function, though it admits this isn’t fully proven. After 15 hours, fasting supposedly boosts growth hormone levels, which helps slow ageing. By 17 hours, fasting starts killing cancer cells. Finally, after 18 hours or more, the body is said to destroy old, damaged cells (called senescent cells) through a process known as autophagy, which may prevent cancer.”
Fact Check
Does fasting for 17 hours cause cancer cell death?
No, fasting for 17 hours does not directly kill cancer cells. Autophagy, which is mentioned in the post, is a process where cells “clean up” damaged parts. While autophagy does occur during fasting, it primarily helps to clear out faulty cellular components, not specifically kill cancer cells. Research on autophagy has been promising in lab settings (especially with animals), but there’s no strong evidence that fasting alone can target and destroy cancer cells in humans. We found a 2016 study involving humans that suggests fasting for 13 hours daily might lower the risk of breast cancer recurrence and related deaths. However, researchers emphasise the need for more trials to confirm if longer overnight fasting can effectively reduce chronic disease risks. Studies on humans are still in the early stages and show mixed results.
We reached out to Dr Pooja Khullar, Radiation Oncologist at Dharamshila Narayana Super Speciality Hospital, New Delhi, for her perspective on whether fasting can cause cancer cell death. She says, “Fasting can benefit overall cellular health, but linking a specific fasting window like 17 hours to cancer cell death oversimplifies the science. Autophagy is a complex process that plays a supporting role in cellular repair, not a direct one in eliminating cancer cells. Claims like these often misinterpret early-stage research. For now, people should focus on proven cancer prevention measures such as maintaining a healthy lifestyle and attending regular screenings.”
We also got in touch with Dr Akanksha Chhabra, Medical Oncologist, Max Healthcare, New Delhi, for her take on fasting for cancer cell death. She states, “Fasting has sparked a lot of interest in the medical community, especially its potential to trigger processes like autophagy. While autophagy helps the body clear out damaged cells, it doesn’t mean fasting directly kills cancer cells. The research we have is promising but largely experimental. At this stage, we cannot recommend fasting as a standalone approach to treat or prevent cancer. A balanced diet, regular exercise, and evidence-based treatments remain the most effective strategies.”
Can fasting for 13 hours boost testosterone levels?
No, there’s no strong evidence that fasting for 13 hours boosts testosterone levels. The idea comes from a few small studies on caloric restriction and hormones, but no direct link has been proven. While fasting might improve metabolic health and weight loss, which can indirectly support testosterone, research suggests it may actually lower androgen levels (hormones like testosterone that affect reproduction and metabolism) in both males and females. This could help women with PCOS improve fertility, but in men, it might reduce testosterone, potentially impacting metabolic health and libido.
Moreover, a 2023 study found that fasting slightly increased testosterone levels in healthy women of reproductive age. However, in women with conditions like hirsutism, irregular periods, or hair loss, fasting had no effect on testosterone levels. Lifestyle factors like balanced diet, regular exercise, and sleep have a far greater influence on testosterone levels than fasting. More studies are needed to understand these effects fully.
Does fasting increase growth hormone levels at 15 hours?
Yes, but the increase may not be as impressive as the claim suggests. Fasting has been shown to raise levels of human growth hormone (HGH), especially after periods of insulin reduction and lower blood sugar. However, claiming this leads to “anti-ageing” effects is an overstatement. While growth hormone helps with cell repair and metabolism, there’s no evidence to suggest it can reverse ageing or deliver major health benefits. We still need more research before we can fully understand its role.
What happens with autophagy after 18 hours of fasting?
Autophagy begins during fasting, but it doesn’t kick in at exactly 18 hours. The idea that autophagy suddenly becomes significant after 18 hours of fasting is misleading. Autophagy does start during fasting, but the exact timing varies from person to person. It depends on factors like metabolism, exercise, overall health, and previous fasting experience. While autophagy has shown promise in studies related to aging and degenerative diseases, its role in cancer prevention is still unproven. There’s no clear-cut time when autophagy “works” in the way people expect.
THIP Media Take
The viral post overstates the benefits of fasting by cherry-picking preliminary research and presenting it as definitive. Therefore, the claim that fasting for 17 hours kills cancer cells is mostly false. While fasting can help with weight management, cellular repair, and metabolic health, there is no clear evidence to support claims that it kills cancer cells in humans, boosts testosterone dramatically, or has strong anti-ageing effects. If you’re considering fasting, it’s important to consult with a healthcare professional to make sure it’s safe for you.
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