New Research Finds Intermittent Fasting Diets Are No Better than Standard Calorie Restricted Diets for Longevity
Fans of intermittent fasting often tout the wide array benefits of the diet strategy. Due to the purported appetite control benefits, many find fasting methods an easier way to achieve weight loss goals, without the necessity for calorie counting. Another effect that many endorse the diet method for, is it's alleged positive benefits on longevity.
Now, a new review has compared intermittent fasting strategies with calorie restriction, to analyse the anti-ageing results.
The Study
The primary aim of the review published in Nutrients was to compare the results of intermittent fasting with non-fasting methods of calorie restriction on ageing related outcomes such as cardiometabolic health, cancer risk and neurocognitive performance in adults. The review also aimed to assess the adherence and long term sustainability of both diet methods.
The Methods
The review systematically searched databases such as PubMed, CINAHL and Google Scholar for relevant trials which took place in August 2023. 30 trials met the eligibility criteria for inclusion in the review. These trials were categorised into intermittent fasting, caloric restriction and combined intermittent fasting and caloric restriction interventions. The review analysed the results of the trials related to weight loss, metabolic markers, cancer risk indicators and cognitive function.
The caloric restriction interventions involved participants eating around 20-25% less than their normal intake. The intermittent fasting interventions involved structured periods of fasting followed by eating within specific windows but with the same total calorie intake as the caloric restriction groups. This is to ensure a fair comparison of the two strategies.
The Results
Body composition: Both intermittent fasting and caloric restriction led to significant weight loss and fat loss. However, intermittent fasting showed enhanced adherence and sustainability compared to caloric restriction, making it a better option for long term results.
Health: Fasting and caloric restriction both resulted in improvements in cardiometabolic markers. This included better lipid profiles, improved glucose metabolism and enhanced insulin sensitivity. IF showed reductions in oxidative stress and inflammation.
Illness risk: Only a few studies addressed cancer specific outcomes, with one using a 'fasting mimicking diet' reporting reduced levels of insulin like growth factor 1 (IGF-1) — a marker associated with higher cancer risk.
Neurocognitive effects: Data on neurocognitive effects were limited. One study indicated that caloric restriction could improve memory and functional connectivity in the brain, while intermittent fasting showed some potential neuroprotective benefits, but more research is required in this area to draw conclusion from this.
The Conclusion
The review concluded that both intermittent fasting and caloric restriction offer significant health benefits, particularly in reducing body weight and improving cardiometabolic markers. Intermittent fasting appeared to have the edge over caloric restriction in terms of long term adherence and sustainability, suggesting that it could be a more useful strategy for managing health and weight in the long run.
However, the evidence on cancer and neurocognitive outcomes is limited, and further research is needed to fully understand the effects of these diet strategies.
What This Means for Us
When it comes to anti-ageing and risk of illness, if we want to take part in a diet, the most important factor is long term adherence. There's no point in starting a diet that makes you miserable or doesn't suit your lifestyle. For this reason, whether you choose to include a reduction in calories by counting them, portion control, or by using intermittent fasting strategies, what matters most is your ability to stick it out consistently.
More evidence supports this research, with a study published in New England Journal of Medicine finding that intermittent fasting was no more effective than non time restricted eating for weight loss and improvements in metabolic health when calories were equated. This doesn't mean that either of the methods are more superior, but that both can be used to support your goals, mostly according to your preferences.
Many proponents of fasting cite 'authophagy' as one of the methods major advantages over other calorie-restriction models. Autophagy is essentially is the recycling of cell components to support normal function and hemostasis of cells, leading to an improvement in health. While many may argue that autophagy is only present during fasting, research has shown that autophagy can be stimulated by every mode of calorie restriction, whether time restricted or not.
So the bottom line is: if your goals involved weight loss for better health outcomes, choose a diet strategy that allows you to maintain a calorie deficit, that you can adhere to consistently. And if in doubt, talk to a registered nutritionist or dietitian to give you guidance on what is right for you.
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