Being so convenient, low carbohydrate-high protein bars are extremely popular with people on a ketogenic diet. The question we had was whether these bars were actually “Ketogenic”? We defined this as the bar having no negative effect on blood ketones. We tested the blood ketone response to popular ‘low carb’ and ‘keto’ bars to know for sure.

This summary of the keto experiment covers the following:

What the Keto Experiment Was and Why We Did It

During a recent Keto London Meetup a small crowd experiment was run with members of the Keto London community. The aim of the study was to test the blood ketone responses to different types of popular low carbohydrate bars.

In other words:

  • Can you eat a low carbohydrate bar and still stay in ketosis?
  • Which bars will keep you in ketosis?

There are a number of popular ‘low carbohydrate-high protein’ bars on the market. Because of this, many people believe them to be ‘keto friendly’. However, this is may not always be the case.

Although maintaining elevated blood ketones is not necessary for everyone, many individuals look to avoid foods that may ‘kick them out of ketosis’. We wanted to test the most popular bars to see whether they really were ‘ketogenic’.

To be a true ‘ketogenic’ food, it should not decrease ketone levels in the blood. Being so popular and convenient, it’s important for people to know what these bars are doing to blood ketone levels.

Previous research looking at similar protein bars showed low protein, fat and carbohydrate-based bars impaired glucose compared to high protein, low fat bars 1.

This was, therefore, an opportunity to compare the “Low Carbohydrate High Protein” bar format to a new “High Fat High Fibre” bar format (The Ketone Bar).

The Ketosource Ketone Bar was previously tested in a Beta Trial on 38 people, showing an increase in ketone levels due to its Ketogenic Profile and its C8 MCT Oil and C8 MCT oil powder content. The same results were expected in this experiment.

How the Experiment Was Run

What Was Tested?

For the experiment we had participants eat 120g (two bars) of their allocated bar. This higher amount was agreed to ensure we got a clear signal of each bar’s blood ketone response.

We randomised nine volunteer participants to one of the three bars:

Table 1: Three different bars used in the experiment and their dosage

How Did We Prepare For The Experiment? Who Did It?

Nine people following a ketogenic diet were recruited in the weeks leading up to the Keto London Community Meetup to take part in the experiment. It was essential that they were following a ketogenic diet in order to test the impact of the bars on a state of ketosis.

They were given a brief overview of what the study would entail and were asked to complete a questionnaire to determine whether they were eligible to take part the week before the experiment was due to take place.

The eligibility questionnaire covered the following areas:

  • Gender
  • Weight
  • Height
  • Any and Which ongoing health issues
  • Any and Which medications and supplements taken
  • Whether participants were on or off a ketogenic diet
  • Whether participants would be in ketosis on the day of the study
  • For the purpose of this study, ‘ketosis’ was confirmed at a blood ketone level of 0.5mmol

How Did We Do The Experiment?

Figure 1. Overview of the Testing Procedure

It was ensured participants were fasted for two hours prior to consuming the bars, and a pre-testing survey was completed by each participant to address potential confounders to the experiment such as:

  • Sleep
  • Energy
  • Illness
  • Weight
  • Current medication
  • Time finished last meal
  • Any pre-test exercise (previous two hours)

Once the questionnaire was complete, baseline resting blood ketone measurements were taken on all participants. This was followed by the consumption of two randomly assigned ‘low carb’ bars.

One hour after eating, further measurements of blood ketones were taken and again at the two hour mark. These measurements were taken to determine the blood ketone response to each bar. Results were analysed using basic statistical tests to compare changes in ketone levels and to identify any significant differences between the bars.

The Keto Experiment Results

The figure below shows the trend towards increased ketones in the Ketone Bar compared to both the Carb Killa Bar and KetoSlim, particularly at 1 hour.

We can see quite clearly a rapid decline in ketones with the KetoSlim and Carb Killa Bar.

Figure 2. Average Blood Ketone Values for Each Bar For 2 Hours After Eating

We also ran statistical tests to see if any results were significant. However, statistical tests showed only a significant effect of time on blood ketones. There was no significant effect related to which bar was eaten. This is likely due to the small sample of participants (N=9).

Individual Responses to the Ketosource Ketone Bar

The results of the Ketone Bar were more variable for each person. For this reason, we examined the data further to map out the individual responses to the bar.

Figure 3. Individual Blood Ketone Responses to Ketosource Ketone Bars

What we can see here is that three out of the four people who took the Ketone Bar had the expected ketogenic response. One person had the opposite response which was unexpected (Person 4 – the dotted line).

Specifically, there were 3 scenarios:

  1. Two out of four people (Person 2 and 3) showed an increase in ketones after 1 hour that then returned to baseline level at the second hour or a steady increase in ketones levels over the course of the two hours.
  2. Person 1 had zero ketones at baseline (0.0 mmol/L). This person experienced an increase in ketone levels over the two hours after eating the 2 bars.
  3. Person 4 (the dotted line) had an unexpected response and saw a decrease in ketones throughout the two hour experiment. This is unexpected because it does not coincide with a previous N = 38 trial or the understood response to a high fat, low carb, moderate protein bar. We want to do repeat tests with this individual to understand A) if it is his typical response, and B) try to identify the reason/ mechanism for his atypical response. This page will be updated later with any further experimental data.

Analysis: What Could Explain These Results?

Differing Ketogenic Ratios

It would have been possible to predict the non-ketogenic responses of the two low carb high protein bars (Carb Killa Bar, KetoSlim) by examining their macronutrient profiles provided in their nutritional information.

The Low Carb High Protein bars have different macro breakdown compared to the High Fat High Fibre bar.

Using the commonly used ketogenic ratio (Fat divided by Carbs + Protein) illustrates the large differences between the bars. A classic ketogenic diet is said to have a ratio of 4.0, while moderate ketogenic ratios are said to be of between 2.0 to 3.0.

Table 2. Nutritional Information of Bars and Calculation of Ketogenic Ratios

Note: Green highlight shows where the bars’ macro breakdowns differ significantly.

The polyols are currently accounted for in the “Carbohydrate” section of nutrition information/ facts labels. However, since polyols typically do not have any impact on blood glucose or ketones it’s useful to remove them.

Using the adjusted ketogenic ratio (without polyols), the Ketone Bar has a moderate ketogenic ratio of 2.0. The other two low carb high protein bars have very low ratios of 0.3. So from a ketogenic ratio perspective, they would be expected to not have a ketogenic response (and thus lower blood ketones).

Ketogenic Profiles and Ratios

To be a true ‘ketogenic’ food, a product should have a ‘ketogenic profile’. It should not significantly decrease ketone levels in the blood.

Although maintaining elevated blood ketones is not necessary for everyone, many individuals look to avoid foods that may ‘kick them out of ketosis’. We wanted to test the most popular bars to see whether they really were ‘ketogenic’.

Following a ketogenic diet is extremely personal. The exact macronutrient breakdown and how you follow it will depend on your goals. Not all foods that are deemed ‘ketogenic’ will fit into the confines of each individually adjusted macronutrient breakdown. Therefore, it is always best to test the blood glucose and blood ketone response to the product before incorporating it into your diet for the long term.

Figure 4. Ketogenic Diet Ratios Vs ‘Keto’ Bar Ratios

The chart above shows a picture of the three most common ketogenic diet ratios, 4:1, 3:1 and 2:1. You can see the approximate breakdown of carbohydrates, fats and proteins for each subtype.

The macronutrient breakdown and profile of each ‘keto’ bar is shown. As you can see, the Ketone Bar is the only bar with a true ketogenic profile which is similar to the 2:1 ratio ketogenic diet subtype.

Non-Ketogenic Ingredients

Going beyond the macronutrient breakdown of foods is often beneficial to understanding their ketogenic profile.

The Carb Killa Bar and the KetoSlim contain ingredients which have previously been identified as not having a ketogenic profile.

The Carb Killa Bar contains maltitol and polydextrose. These are counted as polyols and fibres in the nutritional information and thus were not removed in our ‘ketogenic ratio’ analysis with the adjusted ratio. Neither polyols or fibres were included.

However, previous testing has shown that the polyol maltitol increases blood glucose (and thus would be expected to reduce blood ketones). Similarly, the fibre polydextrose has been shown to both increase glucose and reduce blood ketones.

The KetoSlim also contains maltitol as well as the similar ‘maltitol syrup’. In addition, it contains tapioca starch, an ingredient that may have a non-ketogenic response.

Why Do Ketones Increase for the Ketone Bar?

The Ketone Bar showed an increase in blood ketones for 3 people at 1 hour after eating.

Even ketogenic foods (foods with a ketogenic ratio) do not typically raise blood ketones after ingestion. Instead, ketones rise over time gradually (e.g. over course of a day) in response to having an overall diet with a ketogenic profile.

However, the ketone bar contains C8 MCT oil and C8 MCT oil powder. C8 MCT oil is effective at raising blood ketones (see review of the literature here).

Is Everyone Following a Ketogenic Diet in Ketosis?

Not everyone following a ketogenic diet is actually in a state of ketosis (>0.5mmol blood ketones).

Two participants following a ketogenic diet had blood ketone values of 0 at baseline. Both had not previously tested their blood ketones – but assumed, based on their diet, that they were.

This highlights the value of ‘blood testing’ when following a ketogenic diet. It may also illustrate that people need to follow personalised diets in order to ensure they are in ketosis.

What about Quest Bars, Are They Ketogenic?

Another popular low carbohydrate bar is the Quest Nutrition Protein Bar Range.

Following the experiments above, two members of the Ketosource team tested 120g (2 bars) each to see what their glucose and ketone response would be.

Table 3.Quest Nutrition Bar used in this experiment and its dosage

Figure 5. Average Relative Blood Ketone Values for Quest Bar for 3 Hours After Eating

Figure 6. Average Relative Blood Glucose Values for Quest Bar for 3 Hours After Eating

Quest Bar Test Results

As you can see from the results, both the Carb Killa Bar and KetoSlim had quite a negative impact on both blood glucose and ketone values in the two participants.

The Quest Protein Bar (Choc Chip Cookie Dough Flavour) had a different effect on glucose and ketones. Though glucose increased by over 1mmol in the KetoSlim and Carb Killa Bar, the Quest Protein Bar only increased glucose by just under 0.25mmol.

At the two hour mark after eating, the Quest Protein Bar even reduced blood glucose levels, returning back to baseline at the three hour mark.

Ketone levels dropped by an average of 0.4mmol and 0.65mmol  at one hour post eating for the KetoSlim and Carb Killa Bar respectively. The Quest Protein Bar, on the other hand, had only dropped by approximately 0.2mmol at the one hour mark, with a total drop of 0.3mmol at 100 minutes. This is exceptionally different to the KetoSlim and Carb Killa Bar which had a similar impact on ketones and glucose.

The ingredients in the Quest Protein Bar may be the reason for the more favourable result. Though the Quest Protein Bar does not have a ‘ketogenic profile’, many of its ingredients are ‘keto friendly’, for example, erythritol sweetener and stevia leading it to be the more favourable bar out of the three.

In the next experiment, the Ketosource team members will compare these three bars against the Ketone Bar which has a ‘ketogenic profile’.

Post Analysis – Strengths and Limitations

We tested 120g (approximately two bars of each type) to make sure that we saw a clear effect on blood ketones and blood glucose levels.

We wanted to see if each product had a true ketogenic profile. These effects may not have been apparent enough if we consumed less than 120g.

There was one clear limitation of this bar trial:

As there were only nine participants in this trial, there were not enough people for a meaningful analysis. Future studies should have larger sample sizes. The outcomes and findings of this trial are to inform and encourage the practice of N=1 experiments.

Finally, future research will be a follow-up experiment with a standard dose of 60g or one bar. This will be a true reflection of what most people would consume and will give a realistic assessment of the impact one bar will have on blood glucose and ketone levels.

Final Thoughts

These results show that neither the Carb Killa Bar nor the KetoSlim is ketogenic. To our knowledge, neither of these bars has been tested for ketogenic diet compliance previously.

Nature’s Plus claim that their KetoSlim bar is ‘keto’ and they refer to it as ‘ketogenic’. This is misleading when it A) does not have a ketogenic profile, and B) when tested decreases ketone levels in the blood.

In the case of the Carb Killa Bar, no claims are made by the company as to its ketogenic profile. So it is likely that people have just assumed it is ketogenic based on its low carb profile.

This does not mean these products cannot be consumed on a ketogenic diet, but caution must be taken, especially if the bars become common place in the diet, and if the individual has a specific reason to maintain ketosis.

Given the results for the Ketone Bar were not conclusive further testing and experiments are needed. In particular, follow up repeat testing should be done with Person 4 (the outlier). In addition, a larger well-controlled experiment of N = 20 or more should be designed and run to further validate the results – and understand if some individuals respond differently to it (similarly to Person 4).

Live Video Streams of the Experiment at Keto London

The experiments run at Keto London are streamed live with video on the Keto London facebook page.

Part 1: Starting the Experiment Watch here to see the volunteers complete their questionnaires, take their baseline blood ketone readings and start eating their randomly allocated bars.

Part 2: Results of the Experiment and Discussion Watch here to see the presentation on ‘ketogenic foods’, the volunteers take their next two blood ketone readings and the final results of the experiment are presented and discussed.

Summary: The Takeaways

  • Not everyone who thinks they are following a ketogenic diet is actually in a state of ketosis (>0.5mmol). If you are following a ketogenic diet you should validate it at least once using blood testing (On Call Dual GK Monitor) to confirm you are in ketosis.
  • Neither the Carb Killa Bar nor the KetoSlim is ketogenic by our definition. If you are on a ketogenic diet, you should avoid these bars (and potentially other low carb high protein bars) if you’re looking to maintain ketosis.
  • The Ketosource Ketone Bar is ketogenic (and additionally increases ketones for most people). But, there may be some individuals who respond differently to it. We need to run further experiments to confirm this, and then if some individuals do respond differently, we would need to experiment to identify why these people respond differently.
QUESTIONS: Have you been eating Low Carb High Protein bars and snacks thinking they were keto? What would you like us to test next? Let us know by adding to them in the comments.

Study References:

  1. Williams, G., Noakes, M., Keogh, J., Foster, P., & Clifton, P. (2006) High protein high fibre snack bars reduce food intake and improve short term glucose and insulin profiles compared with high fat snack bars. Asia Pac J Clin Nutr, 15(4), 443-450. , 8