For accessibility related questions, please contact us or visit our Accessibility Statement.

Combine Intermittent Fasting with Any SlimFast Plan

Intrigued by intermittent fasting? You are not alone! Intermittent fasting aka “IF” has become increasingly popular over the last few years as many continue to seek out new solutions for weight loss and weight management. The conversations around intermittent fasting can often revolve around those following a ketogenic diet, but the good news is that you can follow any type of dietary approach while integrating intermittent fasting. SlimFast Plan Consultant and Registered Dietitian, Maryann Walsh explains how any of the SlimFast Plans can be followed in combination with IF.

So what exactly is Intermittent Fasting?  While we want to make sure we are taking in a proper balance of nutrients, generally speaking, intermittent fasting focuses on the when versus the what when it comes to eating. Intermittent fasting creates two windows of time: one for eating and one for fasting and the patterns that they happen in, which we will discuss.


While there are many opinions about what truly defines intermittent fasting (IF), it’s important to note that at the time of this writing, no major governing body in science or medicine has stated a standardized definition for IF. As a result of there being no standardized definition, there are few ways one can approach IF, we’ll briefly discuss some of the more popular types as we explore how the SlimFast plan can be combined with IF.


16:8 Intermittent Fasting

This is where you have an 8-hour window where you can enjoy meals and snacks. This could mean you have breakfast at 10 am, lunch at around 2 pm, and then dinner right before 6 pm, consuming snacks in between the meals to hold you over. This could also mean skipping breakfast and having your first meal at noon and your last meal right before 8 pm. These meals can be anything as long as they fit within your calories for the day, so don’t get too caught up in thinking just because you start your feeding window at noon that you can’t have traditional breakfast foods like eggs and toast. The focus here is on consuming all of your calories within the designated time frame.


12:12 Intermittent Fasting

A 12:12 intermittent fasting pattern is just like the 16:8 pattern mentioned above but allows for a larger eating window. This may feel more natural for most people considering eating time frames like 8 am-8 pm would fit into that 12:12 window.

Any of the SlimFast Plans can be utilized within these time frames discussed above, just consume your 2 meal replacements, 3 snacks, and 1 sensible meal within your eating window. As mentioned above, it’s all about fitting the calories/food intake for the day within that time frame. You could essentially choose to enjoy a SlimFast meal replacement as your first meal of the day or you could choose to have your sensible meal on the plan as your first meal of the day, you can mix and match to make it work for you. You can learn more about the different types of SlimFast Plans and get started by choosing one here!

There are a few other notable approaches to intermittent fasting, however, these involve days where you would be consuming less than 600 calories per day or 0 calories per day, and anytime one is to consume below 1200 calories per day (which is the minimum on the SlimFast Plan) it is recommended to discuss with your doctor.


5:2 Intermittent Fasting

This IF approach involves eating as you normally do for 5 days of the week and then 2 days of restricting calorie intake to 500-600 calories for the remaining 2 days.


Alternate Day Fasting

When one chooses to eat normally one day and then consume 0 calories the next day, alternating between normal days and fasting days.

Pros of Intermittent Fasting

Numerous benefits are discussed when it comes to fasting, some have valid research backing them while others unfortunately, may be hearsay, so it’s important to consider the sources of information when you weigh the pros and cons of fasting. More research is needed at this time, but the research that is currently available suggests that fasting may have a positive effect on one’s immunity and on lowering inflammation in the body.1,2.

When it comes to fasting being beneficial for weight loss there are a few reasons why it may be an effective approach. From a behavioral standpoint, eating your meals and snacks within a strict time window may naturally decrease your overall calorie intake and cut down on night-time snacking (“kitchen is closed” mentality), which can aid in weight loss and often be a great solution for those who derail their progress by overconsuming calories at night. For those following the SlimFast Plan, you would simply make sure that your last sensible meal, meal replacement, or snack takes place before the end of your eating window.

One study showed a decrease in fat mass in those who practiced a 16:8 IF pattern versus those who ate the same number of calories without having a fasting window3. Another study showed a significant weight change in those who restricted nighttime eating versus those who did not4. There is valid reasoning to consider a connection between added benefits for weight loss and IF overall, however, the body of current research as a whole has yet to pinpoint if there is a true benefit to IF when comparing similar calorie intakes to those who do not practice IF5.

So, what does this all mean? While some rumors circulate online and on social media that one can consume as many calories as they want within a time window, the reality is that the restricted time frame lends itself to the reduced calorie intake in general, which is what the true driver for weight loss is most likely in these cases. All of the SlimFast Plans layout a simple framework for consuming a reduced calorie intake each day, so combining them with IF may be a great way to help you stay on track with the plan!

Cons of Intermittent Fasting:

Intermittent fasting may just not be a good fit for certain people. First of all, anybody with a medical condition or that is on medications should discuss with their doctor before even considering intermittent fasting, especially those individuals living with diabetes. In addition, some individuals may be more prone to feeling excessive hunger or lightheadedness if they go for too long in between eating windows, so intermittent fasting would not be a good fit for these individuals as well.

Intermittent fasting has to make sense for a person’s lifestyle. If it is a comforting ritual for you to eat breakfast right when you wake up and this sets you up to feel fueled up for a productive day, then waiting to eat within a permitted time frame most likely wouldn’t make sense or contribute to your quality of life. If you need to lose weight you can still successfully do so by perhaps changing up the types of food you eat or your calorie intake at breakfast versus feeling the need to practice intermittent fasting. For those who are avid gym-goers or participants in sports, depending on the timing of workouts, practice or competitions then IF may not be an appropriate fit for your lifestyle either.


Is There Anything That I Can Consume During My Fast?

This is a common question for those who practice IF or that are considering IF. Just like there are differing opinions as to what type of fasting window is best, there are also quite a few differing opinions as to what is permitted while fasting.

Medically speaking, during a fasting period you would not consume anything with calories except for water, just like when you are told to fast before having bloodwork done.

Certain approaches like the SlimFast Plan combined with IF allow for the consumption of certain things during the fasting window. Water, black coffee or tea, or sugar-free drink mixes are often considered appropriate for fasting because they don’t contain calories (or if they do it’s a negligible amount) and they don’t contain sugar so they won’t affect one’s blood sugar for those following a ketogenic diet.

Additionally, because MCT oil is digested and converted to energy quickly and efficiently with a very low likelihood of affecting blood sugar, it is often suggested that this too is appropriate during a fasting window. Some may choose to add MCT oil to their morning coffee, however when following any of the SlimFast Plans it is suggested that you still add the calories from the MCT oil to your daily intake for the day, 1 tbsp is 130 calories and can be considered 1 of your 3 snacks for the day.


Setting Yourself Up For Success Combining the SlimFast Plan with Intermittent Fasting

As you can see the increasingly popular Intermittent Fasting approach can be combined with any of the SlimFast Plans and for many, this may truly be a winning combination to set themselves up for success! As mentioned prior, you can learn more about each of the SlimFast plans and get started by clicking here, there is a wealth of information here on as well as on the SlimFast Together App. Lastly, the SlimFast Together private Facebook groups will provide you with an amazing community full of tips, advice, and support, you can get the links to join them here.

Wishing you lots of success on your journey!





A consultant of the SlimFast Plan, Maryann is a Registered Dietitian with Bachelor of Science degrees in Biological Sciences and Dietetics and a Master of Food and Nutrition. She has extensive experience working with clients of all ages and from all walks of life, helping them to achieve their wellness and weight-loss goals. Learn more about Maryann.