Intermittent fasting 101: What is it and will it help me lose weight?

In a nutshell, intermittent fasting is just that: fasting intermittently.

You limit calorie intake during certain hours/day or days/week. It's also more of an eating pattern than a diet.

You limit when to eat, and not so much what to eat. This really appeals to people who don’t want to count calories or use their food log to track everything.

Some would say that it's a more natural way to eat because – I mean really – we lived life for centuries without eating every hour on the hour. But now we have access to food (including junk food) all day long – in the pantry, the refrigerator, the coffee shop, the vending machine, the gas station, even the health club or gym.

So, it’s really easy to think that eating several meals a day (plus snacks) may feel more natural than fasting (or taking a break from food) from time to time.

There are lots of variations for intermittent fasting.

They include:

  • 16/8 which is a 16 hour “fast” and eating only within an 8-hour time span (a popular recommended window is 1pm – 9pm).

  • 5:2 days of fasting, where you eat regularly for five days of the week, then take in just 500-600 calories/day for the other two (non-consecutive) days.

  • Stop-eat-stop, where you fast for 24 hours once or twice a week, taking in only water.

Is intermittent fasting effective for weight loss?

It depends.

In many cases, intermittent fasting is like the magic bullet of weight loss and health/wellness. It has additional benefits beyond weight loss, including reducing inflammation, improving insulin sensitivity, reducing cholesterol, improving brain health, protective mechanisms against cancer, and even anti-aging benefits.

There is a lot of science backing the process.

But in some cases, intermittent fasting can actually cause weight gain! I’ll talk about that later on.

How does intermittent fasting work for weight loss?

Intermittent fasting can help you lose weight because it can help you to eat fewer calories AND burn more calories too.

Lots of people say they have success with it. But what do the studies show?

At the cellular level, your body produces the right type of hormones to help break down stored fat as an energy source. In a fasting state, the body produces more human growth hormone, insulin sensitivity decreases, cellular repair occurs, removing old or damaged proteins AND there are changes in genetic expression that promote longevity (aka anti-aging).

It gets better.

According to one review study, intermittent fasting helped people to lose 3-8% of their weight over 3-24 weeks. In this study, people also lost 4-7% of their waist circumference (i.e., belly fat).

Another study of 100 people with obesity showed that after a year, the people who fasted on alternate days lost more weight than people who didn’t change their eating pattern.

BUT … and here’s where it’s interesting … they didn’t lose any more weight than those on a calorie restricted diet. Out of the people who were following the intermittent fasting protocol, 38% of them dropped out because they couldn’t successfully maintain the low-calorie approach.

Taking all of this into consideration, here’s what I think.

Sticking with a diet that is sustainable is one of the keys to successful weight loss. If you can’t stay with a weight-loss diet, you’re less likely to lose the weight and keep it off.

Is intermittent fasting right for you?

Intermittent fasting is not for everyone and it’s really important to understand your current health situation to assess if intermittent fasting is the right approach for you. I recommend you work with someone to determine where you’re at.

Something that is a big trigger for me - "My trainer told me I should try intermittent fasting" (Moshe, if you're reading this, I don't mean you).

Um, no. This is so wrong.

I never recommend that clients jump right into intermittent fasting. I take them through a process of first balancing blood sugar, improving nutrient density and then slowly stretching fasting times in a way that makes sense for your unique lifestyle. It's a safe, easy approach and it helps avoid negative side effects.

People who are underweight or have eating disorders shouldn’t fast. Neither should women who are pregnant, trying to get pregnant, or are breastfeeding.

Other medical or underlying conditions to consider are diabetes, poor blood sugar regulation, low blood pressure or amenorrhea. Also, people taking certain medications can be prone to side effects with intermittent fasting as well.

If you have an autoimmune disease, I don't recommend intermittent fasting. It is more important you increase your nutrition than cutting back on calories. In fact, simply following an anti-inflammatory diet will deliver the same health benefits (and more) than intermittent fasting.

MORE BAD NEWS. In some cases, you can actually GAIN weight when following intermittent fasting.

This is particularly true if you have undiagnosed food sensitivities, gut inflammation, an under active thyroid or adrenals, if you’re drinking a ton of coffee during the “fast’ period, binge eating when you come off your fast, struggling with anxiety or not getting enough sleep. Most of my clients struggle with ALL of the above, and that's something that needs to be addressed first.

Men tend to have more success than women when they intermittent fast. Bless them.

For some women, intermittent fasting can WORSEN blood sugar control and undermine thyroid health so it’s really important that females approach the practice slowly and with some guidance.

One of the reasons people drop out of the intermittent fasting eating pattern is that it’s hard to stick with the fasting part. They eat more than the allowed (low-level of) calories when they’re supposed to be fasting. And when they finish fasting, they may overindulge due to the reaction of the appetite hormones and hunger drive while fasting. Cookies, cakes and croissants?

This will not help with weight loss.

Also, the hours and days of fasting can be very difficult. So, for some of you, having strong social support will be key to those intermittent periods of fasting. Or you may need to adjust the schedule according to your lifestyle.

I also see so many people get soooo caught up in what they "think" they should be doing, feel they have "failed" because they couldn't maintain a standard recommendation that was suggested by god-knows-who, and then they throw it all away or give up after one bad day.

Again, I emphasize … sticking to a (healthy, nutrient-dense) weight loss diet is the key to success. Intermittent fasting may be part of the solution, but you should approach it strategically - both physically and emotionally.


Intermittent fasting is a weight loss trend that seems to work for some people. It can help to lose weight and reduce belly fat, and there are lots of health benefits. You can't argue the science.

But, it isn't safe for everyone. You should get a trained nutritional professional to assess whether or not intermittent fasting is the right approach for you.

Intermittent fasting can also be difficult to stick with. On low calorie days, it can be hard to stick within the 500-600 calorie recommendation. And on some days, frankly, you just need to eat a little earlier in the day, or a little bit more, depending on your level of activity. You need a good understanding on how to adjust without throwing it all out the window.

For the best chance of long-term weight loss success, find a diet that is not only effective but sustainable - sticking with a plan is key to success. Maybe intermittent fasting is part of that process? Maybe you need a revised approach?

What about you? Have you or someone you know tried intermittent fasting? What were the results? Let me know in the comments below.


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DISCLAIMER: Please read the following disclaimer carefully. Vanessa Bond is not a doctor and does not diagnose or treat disease. The information on this website is not intended to replace the advice or recommendations of your primary health care provider and is not intended as medical advice. The information is intended as a complement to existing therapy - not as a substitute. The focus is to educate on how to make better decisions in order to build and maintain better nutritional balance. She and this web site encourage you to make your own health care decisions based upon your research and in partnership with a qualified health care professional.


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