The Latest Dietary Health Advice- Intermittent Fasting for Weight Loss
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Intermittent fasting is becoming popular in the health and diet industry. Rather than restricting how much to eat, food intake is allowable only for a limited period. This can be accomplished as a daily occurrence, such as 12-18 hours of avoiding eating. Other variations of intermittent fasting include food avoidance for a 24-hour period or alternating fasting and “normal” eating throughout certain days of the week, month, or year. The most popular approach appears to be the 16/8 variation, eating 8 hours a day and fasting 16 hours.
I reviewed the definition of intermittent fasting, its variations, and some of the research in detail in Part I. Although there is some impressive evidence in healthy individuals and for specific conditions in supervised settings, it is becoming a general recommendation for all seekers of health.
Recently, I’ve been looking at things a bit more from the lens of healthism and have wondered if intermittent fasting is being used irresponsibly for weight loss and in the wrong contexts.
As stated in Part I, there are concerns with intermittent fasting spurring eating disorders and hormonal imbalances in women. Furthermore, adverse effects can occur in certain individuals with genetic variants who have a hard time breaking down the ketones that the body produces as a result from fasting. Finally, everyone has different genetic tendencies and influences for weight loss, irrespective of food intake.
Below, I continue with my cautions and caveats that anyone should consider before partaking in this new dietary approach.
Five Additional Caveats of Intermittent Fasting
Besides what is listed above, here are five more caveats to consider with intermittent fasting.
1. Extrapolating Responses from Rodent Studies to Humans May Not Measure Up
Concerns with extrapolating research results from our furry friends to humans has many limitations. This is eloquently explained in this review. The authors cited conflicting results in longevity and fasting is not only among studies with differing designs and methods, but, are related to different species, age spans, time periods, and types of fasting:
These results in rodents point to conserved effects of fasting on lifespan, but also to the need for a much better understanding of the type of fasting that can maximize its longevity effects and the mechanisms responsible for the detrimental effects that may be counterbalancing its anti-aging effects. For example, one possibility is that fasting may be consistently protective in young and middle aged laboratory rodents that are either gaining or maintaining a body weight, but may be detrimental in older animals that, similarly to humans, begin to lose weight prior to their death. Notably, whereas bacteria, yeast and humans can survive for several weeks or more without nutrients, most strains of mice are unable to survive more than 3 days without food. The age-dependent weight loss may make this sensitivity to long periods of fasting worse.
This cautionary article states the several other concerns I will discuss.
2. Fad Potential Can Lead to Negative Outcomes
As intermittent fasting is being touted as a “cure-all” in the health-o-sphere, the risk of doctors dismissing some of the legitimacy and benefits ensues, “the baby and bathwater thing.” This could lead to negative outcomes for unsupervised individuals partaking in fasting in whom the method is not appropriate for.
3. Extreme Behavior May Be Highlighted
Fasting may encourage extreme behavior. As stated in the article:
This is reflected in the photos accompanying many recent new articles on “the fast diet” or the “5:2 diet.” Often, they depict people eating heaps of high-calorie, high-fat foods, such as hamburgers, french fries and cake. The implication being that if you fast two days a week, you can devour as much junk as your gullet can swallow during the remaining five days.
As I mentioned above, generalizing one type of diet to everyone discounts the differing responses that can occur based on gender, genetic variations, and unique environmental interactions.
5. Gaps Still Exist in Research
A 2017 article entitled, “Potential Benefits and Harms of Intermittent Energy Restriction and Intermittent Fasting Amongst Obese, Overweight and Normal Weight Subjects—A Narrative Review of Human and Animal Evidence,” went into detail about the gaps that still exist in application of intermittent fasting. The authors stated:
The longer term benefits or harms of IER amongst people who are overweight or obese, and particularly amongst normal weight subjects, is not known and is a priority for further investigation.
A systematic review in 2015, with a whopping three studies, echoed similar warnings:
Beyond efficacy, safety data are critical for the therapeutic application of fasting but are sorely lacking. After many weeks of continuous fasting (∼5–7 wk in healthy adults), fasting converts into starvation, wherein vital organs and muscles are consumed for energy.
Starvation causes excessive weight loss, anemia, chronic diarrhea, delirium, and other adverse reactions and eventually death. Intermittent therapeutic fasting should not have these adverse effects, but it may still cause harm when practiced too frequently or for too many days consecutively.
Commonly, fasting may result in mild adverse events such as headaches, fainting, weakness, dehydration, and hunger pangs. More importantly, excessive fasting could lead to malnutrition, eating disorders, susceptibility to infectious diseases, or moderate damage to organs. In a study of rats, ADF* was found to result in increased left atrial diameter, myocardial fibrosis, and reduced cardiac reserve (51). Whereas left ventricular ejection fraction and ventricle size were not measurably affected by ADF, the observed changes suggest caution in the human application of regimens using frequent fasting (51). It may be that fasting multiple days or successive days per week is too frequent or intense for humans.
*ADF=Alternative Daily Fasting
Future fasting research should determine whether and to what extent fasting regimens are safe. Further research is needed to determine whether fasting is effective for improving health in the general population, higher-risk people, and diseased individuals. Additional knowledge is also needed regarding the mechanisms of benefit and the optimal frequency and duration of fasting in apparently healthy and high-risk individuals. Finally, in deference to the current focus on lower-cost healthcare, fasting has no direct financial costs and represents a nominal savings on food expenses. In summary, intermittent fasting may improve health; however, substantial additional clinical research is needed before advocating its use for health purposes.
Should You Fast Then?
I am an advocate for the right diet for the right person at the right time. This is responsible, lifestyle medicine.
My concern is that taking a dietary approach for healing certain states, and popularizing it as a cure-all, lacks a personalized, common-sense approach. If you do decide to try intermittent fasting, it would be wise to monitor metabolic markers and be followed by a medical professional, at least initially.
I am also weary of promoting disordered eating patterns and normalizing them as “healthy” with intermittent fasting. Could, perhaps unintentionally, this method could be promoting orthorexic or anorexic tendencies? Therefore, if you are doing it for weight loss and approaching it from a disordered thinking pattern, it may not be wise to pursue alone. It may be a better choice to heal your relationship with food and learn how to nurture your body in all aspects, with diet as one of them.
Furthermore, as we become more obsessed with restricting our food and monitoring its intake, we could be perpetuating the very risk factors we are hoping to alleviate, through isolation. Moralizing food can lead to avoidance of gatherings centered around food as celebration. This has been part of cultures for centuries. I will go into this “bigger context” in a future article.
Want some fun ideas for the spooky holiday coming up that will allow you to enjoy some food prep without fear and give you a chance to have fun with young ones? See my three self-care tips in Part I.