This is a summary of the full trial write-up, which can be found here.
The purpose of this trial was to evaluate the effect of consuming Huel, a nutritionally complete powdered food, as the sole source of nutrition for 5 weeks. The trial was known as “Project 100”.
Thirteen volunteers completed the 5-week trial, four of which were considered the core participants (see Figure 1) as they had all measurements recorded including anthropometric and blood measurements, both pre- and post-5-week trial.
The assessor provided each participant with a tailored plan of daily Huel Powder (EU v2.3) intake, with their allocated daily calorie intake calculated dependent upon age, height, weight, physical activity and any weight loss, gain or maintenance goals. Information for this was gathered with the Health and Activity Questionnaire Appendix (pages 2–4).
On the first morning of the trial, participants had their pre-trial fasted blood drawn and anthropometric measurements taken. Participants were instructed to consume a diet comprised exclusively of Huel Powder and water for the entire 5-week period. Details of dietary exclusion criteria can be found in the Appendix (page 1).
Participants had their second fasting blood drawn on the subsequent day to ending the 5 weeks of Huel diet.
Upon completion of the trial, participants were instructed to complete a Post-Trial Questionnaire, providing insights into their experience of following a 100%-Huel diet.
Figure 1: Participant information for the 4 core participants
|Huel usage prior to trial||200 - 400g/day for 1 year||On & off for 2 years||None||6 weeks - 2 meals/day|
|Instructed Huel calorie intake*||2,600 kcal||1,800 kcal||2,200 kcal||1,900 kcal|
|Daily calorie deficit*||0||-500 kcal||-500 kcal||-250 kcal|
The 4 core participants completed 5 weeks following a 100%-Huel diet. There were numerous anthropometric and blood marker improvements reported at the cessation of the trial, and all participants reported a generally positive experience.
Three out of the 4 participants were following a calorie deficit to aid weight loss, all of which achieved this goal by the post-trial analysis.
WHR is a marker for body fat distribution and is a strong independent risk factor for numerous obesity-related diseases such as myocardial infarction, stroke and premature death (4, 5). WHR is considered a stronger marker for these diseases compared with other measures such as BMI (4, 6). All 3 participants that were following a calorie deficit reported an improvement in WHR, thereby decreasing their risk of developing metabolic complications.
The sum of 7 skinfold measurements estimates the percentage of body fat by measuring skinfold thickness at numerous locations on the body (7). All 4 participants showed a reduction in sum of 7 skinfolds post-trial, indicating a loss in subcutaneous adipose tissue.
Although using BMI as a marker does not come without limitations (8), it is used as an additional marker to quantify the tissue mass of an individual, and categorise that individual into either underweight, normal weight, overweight or obese (3). All 4 participants reported improvements in BMI after the 5-weeks’ Huel consumption, 1 of which moved from the ‘overweight’ category to ‘normal’ category.
In all 4 core participants, the cholesterol profile improved with a decrease in TC and a reduction in the LDL:HDL ratio from pre- to post-trial. Huel is a good source of the soluble fibre, oat beta-glucans, which have been reported to lower blood cholesterol and reduce the risk of developing coronary heart disease (22).
Additionally, the fatty acid profile of Huel could be linked to the positive changes in cholesterol status. It has been reported that when monounsaturated fatty acids, also known as omega-9 fatty acids, replace saturated fatty acids, LDL and total cholesterol decrease significantly (16, 17). Huel is a good source of monounsaturated fatty acids, provided predominantly by the oats, flaxseed and sunflower oil.
As a proportion of total energy intake, a high consumption of polyunsaturated omega-3 and omega-6 fatty acids have also been shown to decrease total cholesterol and LDL (23). Huel is rich in omega-3s, predominantly from flaxseed, and omega-6s, predominantly from sunflower oil, at 15.8g and 15.6g respectively per day (amounts based on Huel Powder v2.3 Vanilla).
Uric acid increased in all 4 participants, 2 of which reported post-trial results that were above optimal range. Although participant 13 was not one of the core 4 participants, it is worth mentioning that he has been consuming Huel for the majority of his diet for 3 years and showed uric acid levels that were within optimal range (“used Huel pretty much 100% for nearly 3 years” – Appendix (pages 25–26).
Although most participants reported that the trial lacked variety in taste and texture, the arduousness of completing the trial was considered fairly low, with the average difficulty level being reported as 4.5 (on a scale of 1 to 10, whereby 1 was easy and 10 was incredibly difficult). One participant that scored difficulty as 7/8 self-resolved that this was because he was “constantly hungry, but was on a calorie loss.”
Convenience seemed to have been one of the main positives of following a 100%-Huel diet. It was reported that the trial was “easy & accessible” which helped to improve discipline and “make better choices” about food.
Following a 100% Huel Powder diet for 5 weeks resulted in positive anthropometric changes, such as decreased WHR, body weight and skinfold thickness. Together with notable improvements in blood cholesterol status, these results indicate improvements in cardiovascular and other disease risks.
Uric acid was seen to increase when consuming Huel Powder as the sole source of nutrition for 5 weeks. Individuals who are susceptible to gout should take caution if they have a high calorie requirement and are considering using Huel for 100% of their nutritional intake, and it would be preferential to limit Huel to one or two meals/snacks per day.
All 4 participants reported that they found the trial challenging from a socialising perspective when consuming Huel Powder as their sole source of nutrition. However, the convenience aspect helped participants to avoid unhealthy food options, and all reported that they would continue using Huel as a significant part of daily nutrition after the trial.
Huel Powder can be the sole source of nutrition if consumed at an amount of at least 2,000kcal per day, although this is not something that has been actively recommended. The results of this trial support the claim that Huel Powder can safely be consumed as a total nutrition source. Blood marker results illustrate that following a 5-week 100%-Huel Powder diet is likely to offer health benefits. The results of the trial also support the recommendation that people will benefit from including Huel Powder as a convenient meal alternative to less favourable food choices.
For the full version of Five Weeks on a 100%-Huel Diet please click here.
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