Getting Ready for the DDF 30-Day Challenge [FAQ Part 2]

This section of the DDF FAQs covers everything you need to know about preparing for the Data-Driven Fasting 30-Day Challenge.

2.1  What do I need to buy?

Blood glucose meter 

In the Data-Driven Fasting 30-Day Challenge, you will use your blood glucose to optimise your intermittent fasting routine. 

Test strips are often sold separately.  You will need at least 100 test strips for the Data-Driven Fasting 30-Day Challenge and up to 200 if you want to test more regularly.  

Bioimpedance scales 

To get the most out of the Data-Driven Fasting 30-Day Challenge, we recommend you use bioimpedance body weight scales that track your body fat.  Most modern digital scales will do this.  There is a range of options that have various features.   Many people find the Renpho to be a great option in terms of consistency and value for money.   

Tape measure 

Your waist to height ratio is an excellent indicator of your overall metabolic health, so we recommend you measure your waist each week.   A simple tape measure is an excellent investment.

2.2  Which blood glucose meter should I buy?

If you don’t already have one, there are some nifty high tech and cost-effective blood glucose meter options available.  But given you will be using your glucose to guide your meal timing, accuracy is important.  

A great option in terms of features and accuracy is Contour Next One, which comes with a smartphone app that helps you analyse your data.  It’s everything you’d hope a modern blood glucose meter would be!   

You can even program the app to give you a happy flashing green light when you are below Your Personalised Trigger.  You’ll get a nice dopamine hit from the green light (rather than those less-than-optimal comfort foods). 

2.3  Would a continuous glucose monitor be better? 

Continuous glucose monitors (CGM) are quickly becoming the most sought-after biohacker toy, and here are a few options available. 

The Dexcom G6 is the gold standard for Type 1 Diabetes management and sends a reading to your phone or other devices every five minutes, while the Freestyle Libre is a little bit cheaper but requires you to swipe the reader (or your phone across your sensor). 

A CGM is great if you already have one but may be excessive for what we are trying to achieve with Data-Driven Fasting.  Keep in mind that CGM sensors are not painless to insert, and you will have to change them every week or so.  CGMs are also not cheap over the long term, especially if you don’t have insurance coverage! 

While you can calibrate the Dexcom with your glucometer,  you can’t calibrate the Freestyle Libre.  Most people find that the Libre reads significantly lower than an accurate glucometer.  They also often see different readings when they change sensors, which throws out the data. 

The ultimate goal of Data-Driven Fasting is to retrain your appetite by checking blood glucose when you feel hungry and before you eat.  If you can see your current blood glucose all the time, you’re more likely to eat because your blood glucose dropped below Your Personalised Trigger even if you’re not hungry. 

Excessive focus on minimising the blood glucose rise after meals often leads people to low satiety high-fat foods that will slow fat loss from their body.   As you can see from the charts below, more stable blood glucose does not align with lower body weight or healthier waking blood glucose.  That’s why we focus on reducing your premeal blood sugars in Data-Driven Fasting, which allows you to bring down your insulin and blood sugar across the whole day.

Unfortunately, focusing excessively on your blood glucose rise after meals can drive people to eat more low-satiety, nutrient-poor, high-fat foods.   While fat does not raise your blood glucose much in the short term, excessive dietary fat will stop your blood glucose from returning to below Your Personalised Trigger as quickly (see Want to lose fat? DON’T aim for stable blood glucose! (Why your CGM could be making you fat). 

Your liver will release glucose from storage into your bloodstream to keep your blood glucose stable.  Your blood glucose may even rise in anticipation of food.  Some people get confused when they check their CGM when they’re hungry and later find that their blood glucose has risen by the time they have prepared their meal and are ready to eat.   

Remember, the goal of hunger training is simply to verify your hunger with your blood glucose.  If you can see your blood glucose in real-time, you may be tempted to re-fuel just because your blood glucose drops below your trigger, even if you’re not hungry. 

There are also benefits in the slight hassle of doing the finger prick and recording your blood glucose before eating.  After a couple of weeks, you will only need to check your blood glucose a couple of times a day.  This is much simpler and cheaper than wearing a CGM. 

So, a CGM is great if you already have one or you’re a cashed-up biohacker data geek, but it’s not necessarily better for Data-Driven Fasting.  We’d rather you avoid the confusion that seeing your blood glucose in real-time often causes.    

2.4  How should I adjust my medications when I start fasting?

Medications such as injected insulin will help manage the symptoms of Type 2 Diabetes (i.e. elevated blood glucose) but do little to reverse the underlying cause (i.e. energy toxicity).  Injecting insulin to reduce blood sugars can also make it harder to lose unwanted body fat. 

Injected insulin forces your body to hold fat in storage which can make you hungrier.  As your blood sugar reduces and your body starts to burn off your excess body fat stores, you may find you need to dial back both your basal and bolus insulin

If you are taking any diabetes-related medications (e.g. injected insulin or sulfonylureas), you should pay particular attention to your blood glucose as you extend the time between meals.  It is crucial that you work with your health care team to adjust your dosing to ensure that your blood glucose doesn’t go lower than you feel comfortable with (e.g. below 4.0 mmol/L or 72 mg/dL).  Not only will you feel unwell below this level, but you will also want to eat anything and everything until your blood glucose returns to normal. 

Finding a predictable routine is extremely important, and even more so if you are taking diabetes medications.  If you radically change your eating pattern (e.g. skipping a whole day of eating or multi-day fasts), your insulin needs will plummet, and you will risk hypoglycemia (i.e. low blood glucose).  

Data-Driven Fasting will guide you to make incremental changes to your eating routine, which will allow you to dial back your medications slowly. 

Rather than relying on insulin to keep your blood glucose low, it may be prudent to back off your dosing and allow your average blood glucose to run a little bit higher, at least until you develop a consistent routine and reduce the variability of your blood glucose.   Once your glucose variability reduces, you will be able to tweak your insulin dosing to maintain lower average blood glucose.

2.5   Should I check my ketones when fasting?

As you fast for longer, your blood glucose will tend to decrease.  Your blood ketones (BHB) increase as your body starts to burn stored fat for fuel.  This chart shows how blood glucose and ketones change during a seven day fast.  You can see blood glucose slowly trends down while ketones rise. 

But you don’t need high ketones to be burning body fat.   

In fact, as your metabolic health improves, it’s likely that you will see your ketone levels decrease as the energy in your bloodstream decreases (i.e. from fat, glucose and ketones).  Once you reduce your body fat, any excess energy from your diet can easily be stored rather than overflowing into your bloodstream. 

Ketosis is simply an alternative pathway to fuel your brain and vital organs when you don’t have enough oxaloacetate (from carbohydrates and protein) to allow the fat to be burned in the Krebs cycle

In our Nutritional Optimisation Masterclass, people tend to see their blood ketone values increase for a few weeks and then decrease as they begin to burn more body fat. 

Virta’s study results also showed that, after an initial period of elevated ketones in the first few weeks, blood ketones return to baseline as people lose weight and reverse their diabetes.  When it comes to blood ketones, more is not necessarily better. 

Blood ketones are the storage form of ketones, while breath ketones (i.e. breath acetone or BrAce) is a more meaningful indicator of whether you are burning ketones (rather than forcing them to build up in your bloodstream).  So, if your goal is to understand if you are using ketones for energy (rather than storing them), tracking your breath acetone may be more useful.    

The bottom line is that testing blood ketones is unnecessary and doesn’t provide you with actionable data.  Tracking ketones often leads people to consume more fat than they require in the pursuit of ‘optimal ketosis’.  Ketone test strips are also expensive, and the test results are hard to interpret.  So, unless you are curious because everyone else is doing it, and you have some excess cash to burn, save your money and skip the blood ketone testing. 

2.6  I’ve been doing OMAD/ADF/EF before DDF.  What should I do in baselining?

There are slightly different nuances to the DDF process depending on previous eating habits.  Many people come to Data-Driven Fasting because their One Meal a Day (OMAD), Alternate Day Fasting (ADF) or Extended Fasting (EF) routine has stopped working for them. 

This may be because your metabolic rate has slowed due to a loss of lean mass due to inadequate protein.  While it is possible to get your protein requirements in one meal, it is not easy. 

We recommend trying to hit the (minimum) protein amounts shown in the table (based on your height) for a week in the lead-up to the Data-Driven Fasting 30-Day Challenge.    

height (cm)height (inches)female protein (g)male protein (g)

2.7  Tips for blood sugar testing

  • While most people use their fingertips, they can be very sensitive.  You can get blood from anywhere, including the sides of your finger or the outside of your forearm, which is less sensitive.  You may get slightly different values when you test on different fingers or different parts of your body.  This is not an issue so long as you are consistent. 
  • Make sure you have a sharp lancet (they hurt less). You don’t have to change it all the time, but try a new lancet if you feel it’s hurting more than usual.
  • Some meters (like the Contour Next One) will allow you to add a bit more blood if you don’t get enough the first time without wasting a strip.
  • You only need enough blood to get a test result, so dial back the lancet depth to minimise discomfort but still get enough blood. 
  • Make sure you don’t have food on your fingers when you test. 
  • It will also help if you have warm hands and are well hydrated.  You can try shaking your hands to bring more blood to your fingers first.
  • Before you prick your skin, it’s a good idea to rub your skin a little bit to mobilise the blood.  This allows you to have a lower setting on your lancet and potentially less discomfort.
  • If you get a reading that is significantly different to what you expected, you can retest again.  But after that, just accept it and move on.

Further reading 

To learn more, you can:

Data-Driven Fasting Index 

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