Intermittent fasting has become a fad the last few years in the fitness industry. There are a ton of benefits to fasting (some of which we mention in this article), but some people in the fitness industry have taken those benefits and run with them; selling the latest supplement or program and promising aesthetic results. We want to break down the dangers of fasting when it’s used for fat loss or aesthetic goals without taking your mental or emotional state into account.
Additionally, there can be some great benefits and there is a time and place for intermittent fasting. In this article, we go over both the benefits of fasting (according to science) as well as the downsides of time restricted feeding for fat loss.
What Is Fasting?
Fasting is abstaining from caloric intake for a prolonged period of time. The most common types of fasts are 16 hours of fasting with a 8 hour eating window, 20 hours of fasting with a 4 hour eating window, and more prolonged fasts for 24 hours or more.
Many studies have used an 8 hour feeding window when looking at the benefits of fasting. This 8 hour feeding window has been shown to create a moderate caloric restriction, resulting in improvements of blood pressure as well as weight loss when you’re also restricting calories.
Fasting for longer periods is less tested, and could be the hardest to actually adhere to. Even in the studies where this is done, there’s a controlled environment with incentives to stick to longer fasting parameters, like only eating every other day. That’s just not realistic for most people in real life.
The Benefits Of Fasting
Most studies on fasting and gut health come from mice. But, as far as gut health is concerned, research on mice does show the gut microbiome can see improvements from periods of fasting.
We’ve talked about brown fat vs white fat in our cold therapy blog. But for the sake of simplicity, cold exposure can increase brown fat stores. In recent studies, time restricted feeding has also been linked to increasing brown fat storage vs. white fat storage.
Cells respond to intermittent fasting by engaging in an adaptive stress response. There is evidence that shows in simple terms, a “cleaning” of the cells via what’s called cellular autophagy can occur with fasting protocols.
Clinical trials have also shown fasting can have a positive impact on many health conditions such as obesity, diabetes, cardiovascular disease, cancers, and neurologic disorders.
What You Need To Know About Fat Loss & Fasting
All of the benefits just listed about intermittent fasting have nothing to do with fat loss.
People tend to think fasting is magical for fat loss, just because you’re not eating for a certain period of time. The fat loss benefits come from restricting your actual feeding window, which in turn will cause you to eat less, which is creating a caloric deficit. That’s how fasting indirectly causes fat loss. However, there are a lot of other (potentially better for many people) ways to get into a caloric deficit to experience weight loss.
How To Properly Fast
If you do decide to practice time restricted feeding, focus on building healthy habits elsewhere, so that you’re in a good place mentally to restrict the time you eat during the day. When fasting for the purpose of weight loss, there is danger of creating a restrict/binge mindset and development of disordered eating habits.
If you are considering restricting your eating window, think first about promoting healthy habits at night and in the morning.
For example, some people might find that they are already practicing intermit fasting naturally. If you train first thing in the morning before breakfast, waiting 2-3 hours after waking to eat naturally happens. At the other end of the day, stopping eating 2-4 hours before bed is a proven way to get a good night’s sleep. If you eat and go right to sleep, your body is going to prioritize digesting that food over the recovery process during sleep so you probably won’t get into those deeper sleep cycles. So, if you find yourself waiting a bit to eat in the morning and stopping eating a couple of hours before bed, you are already practicing a form of time restricted feeding that is less regimented than a timed fasting schedule.
Fasting For Women vs. Men
There, of course, is a caveat with fasting in relation to the menstrual cycle. In general, women are far more sensitive to fasting than men. Women operate on a completely different hormonal cycle than men. Pre-menopausal women operate on a 28-35 day cycle, whereas men operate on a 24 hour hormonal cycle.
During the last week or so of your cycle, this time of month is when you want to eat slightly above your maintenance calories. In this week before your cycle, you’re going to be hungrier naturally. Lean into this. There is no need to push time restricted eating because this is a time we need food. Your training should also take your cycle into account as well.
Risks Of Fasting
A common drawback with fasting without the binge/restrict mentality is not getting enough nutrients during the actual feeding window. This could include not getting enough protein and other nutrients to meet strength and muscle growth needs. If that is the case, fasting is not worth it. Eating enough calories and protein on a regular basis is far more beneficial than the potential health benefits of fasting.
Fasting can also promote a binge/restrict mindset regarding food.
If you already have an unhealthy relationship with food and/or body image, fasting may not be ideal.
In our opinion, fasting doesn’t work well for people who initially try it for aesthetic reasons. If you’re considering fasting, also consider your mindset and emotional relationship with food first.
The average person should speak with a professional about what can work for them. There is a lot that goes into nutrition habits, and a lot of it can be really emotional. Restricting in any fashion can be very detrimental to emotional and mental health if you’re not in the correct emotional state.
There are also potential health concerns with fasting. Your doctor may not recommend this at all. You may have blood sugar issues or other health conditions that could be negatively impacted by fasting.
On the flip side, your doctor and you may find that you have health issues that could be positively impacted by time restricted feeding. This is why it’s important to talk to your doctor and do your due diligence if you’re going to implement anything outside the norm of what you typically do.
The Bottom Line On Fasting For Fat Loss
You don’t need to fast to see fat loss results. Most importantly, get cleared by your doctor to ensure you are in good health if you are considering a fasting protocol. Analyze your relationship with food and your motivation behind fasting.
If you are going to fast, you’ll want to start slow with no more than 12 hours, and make sure you plan your fasting times according to your cycle. That can simply be eating your dinner 2 hours earlier, or taking away your snack after dinner. From there, you may consider easing into a 14-16 hour fast if it fits your lifestyle and goals. If you try to do too much too soon, you can potentially get headaches, dizziness, or even nausea. We can’t stress enough to make sure you’re working with your doctor, dietician, or functional medicine practitioner when doing any fasting protocol.
Lastly, don’t be strict with your fasting protocol. Figure out how to make this a part of your lifestyle, which means finding something that doesn’t feel restrictive, and feels like a good choice you can stick to.
This blog is educational and the content is not medical advice, and should not be treated as medical advice. Please consult your physician before making any decision about changes to your diet or exercise plan.
Alirezaei, Mehrdad et al. “Short-term fasting induces profound neuronal autophagy.” Autophagyvol. 6,6 (2010): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3106288/
Liu, Zhigang et al. “Gut microbiota mediates intermittent-fasting alleviation of diabetes-induced cognitive impairment.” Nature communications vol. 11,1 855. 18 Feb. 2020: https://pubmed.ncbi.nlm.nih.gov/32071312/
Li, Guolin et al. “Intermittent Fasting Promotes White Adipose Browning and Decreases Obesity by Shaping the Gut Microbiota.” Cell metabolism vol. 26,4 (2017): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5668683/
Rafael de Cabo, Rafael de. Mattson, Mark P. Effects of Intermittent Fasting on Health, Aging, and Disease. New England Journal of Medicine 2019: https://www.nejm.org/doi/full/10.1056/nejmra1905136