How can we use technology to enable positive behavior change, as opposed to promoting distraction and negative behaviors?

Near the end of last year I decided I wanted to try experimenting with intermittent fasting. Fasting has many reported health benefits from increased energy and weight loss to better cognition and even anti-aging. I am not a complete beginner to fasting. I have a certain tolerance towards restricted eating and skipping meals. In the past, I’ve done multi-day water fasts, which are quite challenging but can also be quite physically and mentally invigorating too.

Fasting can be challenging. Changing such an engrained behavior, like when we eat or what we eat, can be hard. So, as technologist and behavior designer, I’m always looking for ways to support what I do, whether it’s leveraging the latest research findings or trying any number of heath and behavior tracking apps.

Technology can play many roles in our lives, and we often lament the many negative ways our phones and apps distract and manipulate our attention. But by and large technology has had a generally positive effect on us as humans. For example, Google search and the internet enable access to nearly anything you wish to know or learn at the “cost” of only a couple of clicks. Whether it’s how to program a computer or finding a great recipe for vegetable soup, it’s easier than ever to discover a piece of information, learn or even develop a skill.

I strongly believe that we often underestimate and maybe even underappreciate how empowering technology can be in the pursuit of goals. Persosnally, I’ve been exploring and writing about the quantified self and self-tracking for a number of years, and I’ve seen the empowering role that technology can bring to how we understand and see ourself through data and orient our actions and choices through that data and through self-reflection.

In this post, I’d like to show how I used a simple piece of technology like Zero to change my behavior, track my progress and ultimately develop a new habit.

First, I’ll briefly explain what is fasting and some of the reported benefits. I’ll then shift to some of the challenges that come with fasting. We’ll then look at Zero, a freemium app you can use to manage and track different forms of fasting. After, I’ll walk through how I used this app to support my own behavior change, some challenges I faced, and how I developed my current fasting habit (16:8 or 18:7). Finally, I’ll conclude with two critiques and design opportunities for Zero and other behavior change apps.

What is Fasting?

Fasting is the intentional abstention or reduction of any or all food from your diet for a certain period of time. Unlike other diets, it’s not about WHAT but WHEN.

There are two key terms to know about fasting:

  • Eating Window - Your eating window describes the period of time in which you eat.
  • Fasting Window - Your fasting window describes the time period in which you abstain from eating. Essentially the block of time you do not eat.

Along with CR, fasting modifies your eating window, which is believed to play a role in some of the health benefits.

Fasting has been a part of numerous religions and philsophical traditions for ages. Fasting become a popular “hack” in the biohacker and health communities with a number of strong health claims purported. Numerous studies have been done showing the biological effects of fasting and reported benefits too.

Types of Fasts: Prolonged and Intermittant Fasting

Broadly speaking there are two main categories of fasting:

  • Prolonged fasts span more than 24 hours and many protocols span anywhere between 48 and 120 hours.
  • Intermittant fasting (IF) involves reducing your eating window to just part of a day and repeated regularly.
  • NOTE: IF is sometimes referred to as Time-Restricted Eating (TRE).

In general, 12-24 hours of fasting can deplete your stores of glycogen, and reduce blood glucose by 20% or more. Prolonged fasting is fasting for greater than 48 - 120 hours, and intermittent fasting is repeating this cycle on a regular basis.

Here are some common types of prolonged fasts:

  • Absolute fast or dry fasting - abstinence from all food and liquid
  • Water Fast - abstinence from all food but still drink water (optionally some also drink non-sugared coffee or tea)
  • Monk Fast - 36h fast promoted by online group called WeFast. Most proponents do their last meal on Sunday night and then do their next meal on Tuesday morning. Water only during the fast.
  • Eat-Stop-Eat - involves fasting for 24 hours, once or twice a week, for example by not eating from dinner one day until dinner the next day.
  • 60-hour fast - Last meal on Sunday night, next meal on Wednesday morning. Water only during the fast

There are a lot of different IF approaches. Here are a few noteable examples:

  • 16/8 or 16:8 Method - skipping breakfast and restricting your daily eating period to 8 hours, for example from 1 pm to 9 pm. Then you “fast” for 16 hours in between.
  • 17:7 Method
  • OMAD (aka “one meal a day”) - spans roughly 22 hours of asting and one or two hours of eating.

An alternative to fasting developed by Valter Longo and others is the fast-mimicking diet, which is a high protein, low carbohydrate, high vitamin, controlled calorie diet. It is believed to activate many of the same metabolic pathways as fasting but is easier to maintain and has less negative side effects.

What are some of the benefits of fasting?


At its core, a fast involves caloric restriction (CR), which forces your body to burn an array of its natural food reserves and convert from utiliizing glucose or blood sugar to burning fat. Several biochemical and metabolic pathways are activated through fasting. Fasting’s caloric restriction and modified eating window are believed to activate various biological processes that remove toxins, promote longevity, improve cognition and various other reported benefits of fasting.

In my resarch, some of the positive effects of fasting include:

  • Longevity: Rat studies increased life span on caloric restriction and age related biomarkers decreased too. This is generally linked with inhibition the mTOR pathway, stimulation of autophagy, and ketogenesis.
  • Metabolism: Fasting affects insulin resistance and obesity biomarkers and is used as treatment for hypertension. Also shown to reduce risk of diabetes.
  • Immunity and inflammation: Improves cell turnover in certain immunity cells and reduces certain inflamation markers. For example in rat studies, fasting showed a major reduction in the incidence of lymphomas and delayed spontaneous tumorigenesis.
  • Cancer: Fasting can have positive effects in cancer prevention and treatment.
  • Ketosis (which is considered an important indicator of autophagy)
  • Cognition: promotes increased neuron production (neurogenesis) and signaling molecules that promote neural health and function (brain derived neurotrophic factor (BDNF), glutamate, insulin, and GLP-1).

What are some of the challeges associated with fasting?

If you are a complete beginner to fasting, you are likely to face a number of biological, social and even habitual challenges with fasting.

For example, even after a couple hours fasting, you’ll likely feel hunger and a somewhat instinctual desire to grab a snack. For longer fasts, especially multiple day fasts, you’ll inevitably feel hunger pangs, which are physical sensation. You might also become light-headed or even a bit irritable while fasting during certain periods. The timing and nature of these effects will vary according to how long it takes your body to utilize all of its stored glucose and convert to fat burning.

If you are in a relationship or family situation, modifying when or how your eating can create some challenges too. It can be hard to explain why you aren’t eating to a non-faster, and you or your partner might feel loneliness or rejection when you skip a shared meal with a family member.

Personally, I find the biggest challenge to be my own habits and routines. Having spent an entire life eating breakfast, lunch and dinner (as well as regular snacking), it is tough to not habitually want to eat at certain times of the day. It almost seems like my mind and body can’t hlep but reach for something to eat at certain times of the day.

I find that increasing the availability and intake of water, tea or coffee helps a lot during these momenets. Even if it isn’t food, somehow a drink of water or tea seems to help me.

In spite of these challenges, fortunately, human evolutionary biology is fairly adaptive and well-equipped towards missing a few meals. We can all handle a fast. Frankly up until a few generations ago, our ancestors could rarely guarantee a single meal per day, let alone 3 meals. So in most cases, you are completely safe to fast, either for part of a day or even for several days.

While admittedly it might take some trial and error, there is a good chance you will be able to train your biology to handle fasting (and you might even come to enjoy it, as I do). I find that I gain a certain creative energy and focus by fasting. Not having to prepare meals or shopping for a certain period can be a de-stressor and time-saver as well.

Chief Challenge with Fasting: Behavior change itself.

So besides the hunger pangs you will occasionally encounter and social challenges that come from skipping meals with friends and family members, what do I view as the main limiting factor to fasting?

I’d argue that the main challenge with fasting is behavior change itself.

Even though I’ve managed to change many of own habits and routines, like running and the content of my diet, change, pursuing a goal or habit can be hard. It can be really challenging to modify such a strong routine, like the food we consume or eating three meals a day. For many of us, everyday we wake up, we make breakfast (along with our coffee or tea), and we eat. A lot of life revolves around these

Assuming you can start fasting in some capacity, there is also the simple organizational and memory challenge with remembering how long you have been fasting and how far away you are from your fasting goal. Once a bit of hunger hits or instinct to grab a snack kicks in, your good intentions can falter.

So, how can technology and techniques from the social sciences support us in setting, pursuing and developing a new habit like fasting?

Let’s look at Zero, an app focused on helping people fast.

Zero: A fasting tracker for enabling self-awareness and “nudging” behavior change

At its core, Zero is a pretty simple app. While I previously used an older version of the app that was free and even simpler than the current version, basically Zero is “just” a fasting tracker.

Here is how it works:

You log when you start your fast and you record when you finish. You can also set a fasting goal or how you want to fast for. The app then gives you a countdown time to reach your fasting goal.

After you complete a fast, the app tells you a few statistics, like fasting duration and even an estimate on how long and which metabolic fasting zones you were in. Over time, you can look at certain trend lines.

Originally the app focused on just tracking your fast, but the new app added a nice addition by also tracking and showing your eating window.

Here are what the core screens look like:

While I’m not sure how validated the fasting zones are since you are not logging blood glucose levels or ketones, it is interesting to see how the app presents a 17-hour fast as different zones, like anabolic, catabolic and fat burning.

Besides Zero’s two primary functions, tracking your fast and tracking your eating window, the app provides notifications and some ways to log how you are feeling during your fast. There is also a pretty extensive on-boarding and goal setting components that allows you tailor the type of fast you start with and develop a learning path towards eventually completing longer and longer fasting windows.

Developed by top health and longevity experts, the app positions itself as a tool to help you fast and reach certain goals like lose weight or gain health. Nevertheless, I’d primarily label Zero, a behavior change health app.

If you are looking for a tracker and a way to keep yourself accountable, then Zero could be a good fit. There is also a nice library of articles and videos to help you learn some of the terms and decide on the right way you want to fast.

How I Learned to Fast with Zero in 6 weeks

The primary motivation I had for using Zero in the past and during this recent experiment was self-tracking. I wanted to measure the duration of my fast and have some data to back up what I was doing.

While I didn’t originally think of this as a habit tracker, I think this is one of the functions the app provides. The app makes is easy to log your fasting time, shows your tracking in statistics and charts and lets you download your data.

It is commonly said that it takes at least 21 days to develop a new habit. The reality, according to research, is that habit formation depends on how hard the habit is, and, by most accounts, it is now believed that it takes on average 66 days to develop a new habit. Measured in terms of automaticity (i.e. how automatic the target behavior feels), habits can take weeks or even months to develop.

As a long-time writer and pursuer of new habits and goals, I’ve pursued and added many new habits to my life, like running, time tracking and task management. I’m a big fan of using technology to support many aspects of habits and goals.

Overall, I think Zero provided a good way to support and track my goal of developing this new habit of fasting. Using Zero as well as some other techniques, I more or less created a new habit for my current intermittant fasting approach (16:8 or 15:9) in about 5 or 6 weeks. My goal wasn’t strict adherance to daily intermittant fasting, so I often would eat a late breakfast on the weekend.

As a long-time self-tracker, I’m a big fan of the charts and graphs the app provides to help me “see” my fasting over time:

For example, as you can see from the data, during the bulk of my habit building phase, I generally did a good job of regularly hitting my 16 or 17 hour fasting goal.

The reminders were useful early on as well since they provided a nice hint of my progress each day and gave me a chance to check-in with myself. Initally I liked the notifications since they were great beginner reminders, but eventually the frequency and type of notifications was a bit much and I ended up disabling them. It would be great to have a slightly more personalized or adaptive experience around these notifications.

Conclusion: Behavior Change Design Opportunities: Changing Tracking Modality, Support Data-Driven Reflection

In this post, we looked at fasting, different types of fasting and some of the reported benefits. We then dug into Zero, a fasting tracker that also can help enable behavior change.

In general, having a timer with stats worked really well for me as a self-tracker and matches well with some key aspects of behavior change techniques too. If you are new to fasting or using technology to augment your pursuit of goals, Zero could be a useful way to start tracking your life.

All in all, I think Zero is a well-thought out and well-implemented health app. It provides learning materials for getting started with fasting. It has an evolving product experience around increasing the duration of your fasting over time.

Ultimately through its fasting and eating window tracking, Zero encourages you to set a goal and then track your progress until you reach a goal. I think the app does a good job of weaving in several research-backed behavior change techniques found in social psychology, like goal setting, implementation intentions, and tracking goal progress.

As a UX designer and behavior change designer, what are some of the issues I see and experienced? How might Zero work better for behavior change and self-tracking?

My two design critiques of Zero boil down to:

  • Supporting an alternative modality for tracking fasting after habit formation.
  • Enabling data-driven reflection using experience sampling.

For the initial goal setting and habit formation period, Zero worked great. I liked the granular level it supported fasting tracking. It makes a lot of sense to actively tracking each and every fast as you are getting used to fasting. This level of self-awareness was important and I think the reminders were encouraging.

All told, I probably used Zero every day for for about 7 or 8 weeks. My initial utilization period focused on just figuring out the start and end of my intended fasting window. During this period, the timer was useful to helping me push through an extra hour or two during my fasting window and know when to end a fast. In the end, once I had rough times I wanted to hit for my fasting, i.e. 12 noon to start of my eating window and 8pmto start of my fasting window, I no longer found the tracker and timer that useful or needed.

Unfortunately, once I had largely developed my fasting habit, I didn’t really want to track my fasting with such granularity or with such a time committment. It just felt like another thing I would need to manage and think about.

After habit formation, it would have been nice to transition my utilization from such a granular tracker to general check-in tracker. For example, instead of tracking exactly when and how long I fasted on each and every fast, I’d rather be asked daily if I did my 16 hour fast or once a week how many how many times in past week have I fasted? This shift in track in tracking granularity would have encouraged me to keep using the app.

When you start a fast with Zero, you are given a prompt roughly 2-3 hours after starting to log your mood. As a rule this can be a helpful technique to check-in and log how you feel. Unfortunately the default timing of the mood tracking missed a big opportunity to measure experience over time. I would have loved to see some form of experience sampling. As I go into detail on how to track flow, experience sampling is a semi-regular way to measure how you feel and can provide a more nuanced portrait of your mood, physical or mental state over time. It would have been nice to have seen the mood tracking utilized in a way that helped me think and reflect on my own fasting experience.

Along with experience sampling, I would have loved a simple reflection or journalling component as well as a way to see how my mood tracking correlated with different stages of my fasting. I’m currently working on a reflection-centered meeting management product, and my collaborator and I have uncovered a general lack of inviting users of productivity, health and other products to engage with their data and gain a sense of empowerment from that engagement. Regardless of the specifics, I would love to see more attention put towards integrating how a faster sees themselves through check-in’s and journalling.

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