Intermittent fasting for weight loss is trendy in the world these days. If you’ve followed me for a while, you know how I feel about weight loss trends. There’s no “magic” weight loss plan or diet that reduces the effort it takes to lose weight and keep it off for good. It does not exist.
The diet industry is a multibillion-dollar industry. It’s in the business of selling you something and getting you to buy something over and over again.
The truth is permanent lasting weight loss comes from a small calorie deficit, eating more nutrient dense foods that balance metabolic hormones, moving your body more, working on your mindset (including managing your lifestyle and stress) and having a support and accountability plan.
I’m not closed minded. I’ve just coaching many women to lose weight and know what works and what does not work, and what does not work are one size fits all diets and diet trends. They are never worthy of your time or energy.
Intermittent fasting for weight loss is something I’m frequently asked about from my weight loss clients so here’s what you need to know.
What Is Intermittent Fasting?
Intermittent fasting is limiting the hours of the day during which you are eating. The idea is to abstain from eating to maximize fat burning capabilities in the body.
The most popular intermittent fasting promotes a 16:8 schedule, meaning that you fast for 16 hours and eat for 8 hours (i.e. 10am to 6pm or noon to 8pm).
Other types of intermittent fasting include:
- 5:3 - eating normally 5 days per week then eating 500-600 calories 2 days per week
- The Warrior Diet – fasting throughout the day then eating one large meal at night
- Eat-Stop-Eat – 24 fast once per week
Every human on the planet fasts already when they sleep. The word breakfast comes from two words - break and fast or break the fast. The word breakfast literally means you’re breaking the fast. So, everyone already fasts when they sleep.
Fasting is something that’s truthfully been going on since we were primal beings. When there was no electricity, it was rare for humans to eat before sunrise or after sundown. Many religions have also practiced fasting throughout the years. Fasting is not new to humans. The question posed for this post is – is it worth your time and effort for weight loss?
How Do You Intermittent Fast?
- Implement a fasting window that works for your lifestyle and do not eat during that window. I recommend starting with 12 hours, so if you finish eating at 8pm, you would start eating again at 8am.
- During your fasting window, you can consume water, herbal tea, and black coffee. Note that adding cream or sugar to coffee or tea technically means you are not in a fast.
- During your feeding window, you eat your meals and snacks. You get to choose what you eat during that window, but as I’ve stated MANY times if you’re not eating to keep your metabolic hormones balanced, keeping yourself in a calorie deficit OR you’re eating fast foods/convenience foods than any potential weight loss or health benefits from fasting will be eliminated.
Benefits of Intermittent Fasting
There are several health benefits to intermittent fasting. Here’s a few:
- Increased Insulin Sensitivity – Insulin resistance means your blood sugar is less stable leading to long-term health conditions like type 2 diabetes, fatty liver and metabolic disorders. Most individuals who are overweight are insulin resistant. Fasting has been shown in studies to improve insulin sensitivity, but the majority of these studies are done on men NOT women. There are very few studies done on women.
- Improved Digestion – It is theorized that eating less frequently is actually better for your digestion overall. The theory is the gut never has a chance to repair when you’re constantly eating. There’s no scientific evidence I could find to support this theory.
- Improved Body Composition – Once the body uses available energy, it will begin to burn fat as energy. This is knowns as “ketosis” where the body utilizes stored fat as fuel. Many studies show that fasting may not decrease overall body weight but does reduce body fat and change body composition. Interestingly, most of these studies are done on men not women.
- Possible Disease Prevention – Risk factors for type 2 diabetes, heart disease, cancer may improve somewhat with fasting. This is believed to be due to improved insulin sensitivity and consequently, the reduction of inflammation as a result of less insulin.
Contraindications of Intermittent Fasting for Weight Loss
Unfortunately, there are many drawbacks to intermittent fasting. Here’s a few:
- Your metabolism may slow down – Research shows the metabolism adapts down with long-term caloric restriction. Fasting can be a way to achieve caloric restriction and if you’re skipping meals and not fueling your body properly then the metabolism will slow down to conserve energy. That means you’ll burn fewer calories and start gaining weight.
- Weight Gain – If the metabolism does slow down, this causes changes in hormones insulin, leptin and ghrelin to increase cravings and fat storage, so you eat more food. The hunger will be so intense that no amount of willpower will allow you to resist it. When the body gets to this state, the body will crave high calorie foods and overconsuming your total daily calories will be very easy.
- Females are less likely to be successful at fasting for weight loss - In fact, the majority of studies have been done on men not women. The female body is highly sensitive to stress. Caloric deficits, fasting, too much exercise, too frequent dieting, too much life stress etc. are viewed by the female body as threats. The female body is designed for reproduction so any type of stressor can easily shift the female body into fat storage. If you’ve done fasting and gained weight even in a caloric deficit, this may mean your body is trying to protect you.
- Low Blood Sugar – Blood sugar sensitivity differs person to person, but for those who have difficulty regulating their blood sugar (i.e. diabetics) can experience low energy, fatigue, brain fog etc. This leads to hormonal changes that increase your cravings for high sugar foods. As mentioned earlier, fasting research does show improvement with insulin sensitivity. However, improved insulin can be achieved with any regular calorie deficit focusing on nutrient dense foods.
- Hormone Imbalances Can Be Exacerbated – If you are a female with imbalanced hormones, fasting is likely to make it worse. Too much calorie restriction or fasting for too long can lead to amenorrhea (lack of menstruation) in females, and studies in rats show that fasting leads to everything from decreased ovary size to “reproductive shutdown”. Hormone imbalances are not the case for men and fasting.
- Exercise and Fasting May Lead To Muscle Breakdown - Research shows that fasted exercise is great for promoting fat burning. However, the body cannot build muscle (anabolism) unless you refuel soon after a fasted workout (within 30 minutes to 1 hour is what I recommend). Not refueling leads to muscle breakdown (catabolism). So, being smart about how you work out, fast and refuel is key to whether or not you get the benefits of a fasted workout.
- Fasting Can Promote Unhealthy Eating Behaviors - Those with a history of disordered eating, emotional eating, frequent dieting or excessive exercising should not impose a fasting window. Instead, I encourage you to listen to your body and fueling it instead of imposing a fasting limitation.
Does Fasting Work for Weight Loss?
Weight loss is achieved by being in a consistent small calorie deficit. Fasting only works for weight loss if you are eating in a calorie deficit.
If you fast for 16 hours, then feel so ravenous that you binge and snack your way through your feeding hours fasting is not helping you – in fact it may be creating a disordered relationship with food. What I commonly see women doing is skipping breakfast and calling it fasting. This is not fasting. It’s skipping breakfast.
This study done on women compared women fasting versus women in a caloric deficit. The women fasting experienced increased hunger and cravings due to the effect on metabolic hormones fasting had on them; however, the women in a caloric deficit did not experience the changes in hunger and cravings.
It’s much easier to lose weight when hunger hormones are balanced. So, this study reminds us that hormones are key to weight loss and even something like intermittent fasting does not yield a shorter route to losing weight.
The bottom line is there’s nothing magical about fasting for weight loss. In my experience working with women, they start losing weight, get a resurgence of energy, less hunger and fewer cravings when they stop doing intermittent fasting. They get results because they’re eating to keep their hunger hormones balances and they’re in a calorie deficit.
The female clients I work with have done every diet on the market, are frustrated and confused by nutrition, have a high stress life, have imbalanced hunger hormones and are frequently experiencing bouts of eating high-sugar, high-fat and high-carb foods. I’m not going to add more stress to these ladies by having them do something like intermittent fasting which doesn’t have significant scientific research that supports it for permanent weight loss for women.
How Do You Know If Intermittent Fasting Is Working for You?
You drink black coffee all morning to suppress your appetite, so you don’t break your fast. --> Intermittent Fasting is not working for you.
You fast for 16 hours then can’t stop eating the rest of the day because your hunger is out of control. --> Intermittent Fasting is not working for you.
You eat “good” for a few days on your fast then suddenly you overeat sugar or fatty foods. --> Intermittent Fasting is not working for you.
You fast, are eating 1200 calories daily and are gaining weight. --> Intermittent Fasting is not working for you.
Can You Lose Weight Without Intermittent Fasting?
Yes, you can lose weight without fasting and here’s why:
- Weight loss comes from a calorie deficit and does not depend on the time of day you eat.
- The benefits of intermittent fasting can be achieved with traditional calorie restriction and eating more nutrient dense foods.
- The most important factors for weight loss are a small calorie deficit and balanced hunger hormones. When you eat or when you don’t eat does not matter for weight loss.