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Should I Be Intermittent Fasting to Lose Weight?

Updated: Feb 16

By Jenna Cutler

NextGeneration Nutrition

clock in plate

Intermittent fasting (IF) seems to be written all over our modern world’s exercise and diet culture. Even those who don’t practice a fasting regiment themselves are intrigued by its growing popularity. So what lies behind IF’s ambiguous yet appealing name?

Defining Intermittent Fasting

It’s important to note that IF is not a diet. Rather, it is an eating pattern that incorporates designated time frames for fasting and eating throughout the day or week. One’s personal fasting and eating times may vary based on which IF method one chooses to follow. Three common methods include:

  1. The 16:8 method

  2. The 5:2 method

  3. Alternate-day fasting method

The 16:8 Method

The 16:8 method is the most traditional IF method. As its name suggests, 16:8 has two daily windows: 16 hours for fasting and 8 hours for eating. During the fasting period, you abstain from eating or drinking anything that contains calories in order to put your body into a fasted state. Drinks such as water or black coffee/tea, however, are permitted. After 16 hours of fasting comes the 8-hour eating window. This is when you consume all of your macronutrients for the day before entering the next fasting period. Here is a typical 16:8 schedule:

  • 7:30 am: Wake up

  • 7:30am-12:00pm: Fasting window (only water, coffee/tea)

  • 12:00pm: Meal 1

  • 5:00pm: Meal 2

  • Before 8:00pm: Meal 3

In this schedule, you fast from when you wake up until noon. Noon until 8:00 pm is your eating window. Adding snacks or changing meal times depending on the day is acceptable, as long as eating only takes place within the eating window. Once your 8-hour eating window closes for the day, you return to fasting until 12:00pm the following day.

While other diets can set rigid eating constraints, the 16:8 method is based on a time-restricted eating schedule where you can choose any 8-hour window to consume calories. Reducing the number of hours that you eat during the day can help you consume fewer calories, leading to weight loss, lowering blood pressure, and preventing hypertension. However, consuming too many calories or unhealthy foods within your 8-hour eating window will nullify the positive effects linked with the 16:8 method. It is important to eat normal amounts of food within your 8-hour eating window.

vegetable and spoon in plate indicating clock

The 5:2 Method

While the 16:8 method pertains to hours of the day, the 5:2 method is associated with days of the week. Simply, 5 days of the week are spent eating normally without restricting caloric intake. On the other 2 days, you reduce your caloric intake to ¼ of your daily needs. Someone’s 5:2 schedule might look like this:

  • Sunday, Tuesday, Wednesday, Friday, Saturday: 1,800 calories per day

  • Monday, Thursday: 450 calories per day

Research shows that the 5:2 method is just as effective as the 16:8 method for weight loss, prevention of heart disease, and blood sugar control among those with Type 2 Diabetes. It also provides flexibility because you can choose which 2 days to fast and there are no regulations on what or when to eat on the 5 eating days. However, it’s still crucial to eat healthy and balanced meals on your eating days in order to see results. This method is not for everyone as cutting down to 450 calories per day is difficult and could make you feel lightheaded or dizzy. It is recommended to talk to a doctor before starting the 5:2 method of IF.

Alternate-day Fasting Method:

On an Alternate-day fasting plan, you fast every other day and can eat anything at any time on the eating days. Modified versions of this method include consuming 500 calories on fast days, while more extreme versions implement consumption of zero calories on fast days. Alternate-day fasting trials for 3-12 weeks long appear to be effective at reducing body weight (3%-7%), body fat (3kg-5.5kg), total cholesterol (10%-21%), and triglycerides (14%-42%).

This method is easy to remember and follow but can be difficult to fast completely for 3-4 days of the week. New intermittent fasters should start with a modified Alternate-day fasting plan in which they can consume 500 calories on their fast days. It is also important to not overeat on your eating days in order for the method to work.

Weight Loss and IF:

strawberry and watermelon slices in plate with clock

All three methods discussed above include different windows for fasting or reduced caloric intake. Unless you overeat during your eating periods, weight loss will occur if a caloric deficit is practiced regularly. Studies show that intermittent fasting reduces body weight by 3-8% over a 3-24 week time period. This weight loss rate is approximately 0.55 lbs-1.65 lbs per week.

Additionally, IF has positive hormonal effects that also work to promote weight loss. The body stores energy (calories) in body fat. So when in a fasted state, your body must adjust to its reduced supply of accessible energy and turn to the energy stored in fat instead. Hormones such as insulin and norepinephrine are affected while fasting. Insulin levels increase while eating and decrease while fasting. Decreased levels of insulin promote fat burning. Norepinephrine is a neurotransmitter that gets sent to your fat cells while fasting helps break down fat cells into 3 fatty acids that the body can use for energy.

How to Successfully Go About Intermittent Fasting

There are several things to remember if your goal is to lose weight through intermittent fasting:

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  • Nutrients: The foods you eat still matter despite your time spent fasting. Make sure to eat fruits, vegetables, healthy fats, grains, and protein to reap the benefits of intermittent fasting.

  • Calorie control: Calories still matter. Try to eat normally within your eating windows or on your eating days, not overcompensating for the fasted days.

  • Patience and consistency: Your body might take a longer time to adjust to an intermittent fasting schedule. But sticking with it and being consistent with your eating schedule will help make it easier for your body to adapt.

  • Exercise: It’s important to incorporate exercise into your weekly routine in order to maintain healthy muscle mass while losing fat through intermittent fasting.

**Consult with your health care professional before starting any of the intermittent fasting methods as this lifestyle may not be beneficial for everyone. **


Jessica Mantell M.S., C.N.S., L.D.N.

CEO & Founder of NextGeneration Nutrition

Jessica Mantell, CEO & Founder of NextGeneration Nutrition

NextGeneration Nutrition believes that better health should be accessible to everyone and that we all are able to improve our health through good nutrition, physical activity, and lifestyle change. We do not support setting shame-based goals but encourages embracing our bodies, genetics, and personality. Our philosophy is abandoning the “One Size Fits All” mentality to create a personalized wellness plan based on your biological makeup and your lifestyle.

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1 Comment

Juli F
Juli F
May 30, 2021

I didn't know the different types of intermittent fasting! Thank you for the information Jesicca!

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