The Science

The Fast 800 is the umbrella term for a healthy lifestyle based on scientific evidence, encompassing diet, movement and mindfulness. 

So much of the noise in the diet and health industry is based on “fad” and “yo-yo” dieting which has created a legacy of poor health and negative experience.

Our commitment is to act with integrity, while being guided by actual science and data, to do the best for our customers and community, so that we can all live healthier lives.

800 Calories and Rapid Weight Loss

The DiRECT Trial

Background: A major study that explored the power of an 800 calorie/day diet for 3-5 months to achieve major weight loss and remission of type 2 diabetes. The study divided participants into two groups: the first group (the intervention group) were placed on an 800 calorie diet and the second group (the control group) were given the usual NHS treatment for type 2 diabetes.


A staggering 46% of participants in the intervention (800 cal) group achieved remission of diabetes, compared to only 4% in the control group. Weight loss statistics were equally impressive; after 12 months, 24% of the 800 group had still lost more than 15kg of weight, compared to 0% in the control group. Not only did they lose more weight, but also kept more of it off.

Find out more: Lean, M., Leslie, W., Barnes, A., et al. (2018). Primary care-led weight management for the remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. Lancet, 391(10120), pp. 541-551. View study

View Study


Background: Obese and overweight participants were assigned to either an 800 calorie/day diet for 8 weeks, or a control group who were given the current usual care support. The 800 cal diet was coupled with behavioural support and a structured food reintroduction.

Results: The intervention (800 cal) group lost over three times more weight than the control group, losing an average of 10.7kg 12 months after starting the programme. 45% of participants in the 800 cal group lost more than 10% of their initial body weight. The intervention group also showed more improvements in various other health markers than the control group.

Find out more: Astbury, N., Aveyard, P., Nickless, A., Hood, K., Corfield, K., Lowe, R., Jebb, S. (2018) Doctor Referral of Overweight People to Low Energy total diet replacement Treatment (DROPLET): pragmatic randomised controlled trial. BMJ, 362:k3760.

View study


Background: The PREVIEW lifestyle intervention study  is, to date, the largest, multinational study aimed at preventing type 2 diabetes.  2,326 pre-diabetic patients from eight countries followed an 800-calorie diet for eight weeks as part of a longer term weight loss management and diabetes prevention study.

Results: After eight weeks, participants had lost an average of 11kg, and experienced an average reduction of 10cm in waist size.

Find out more: Christensen, P, Meinert Larsen, T, et al. (2018), ‘Men and women respond differently to rapid weight loss: Metabolic outcomes of a multi-centre intervention study after a low‐energy diet in 2500 overweight, individuals with pre-diabetes (PREVIEW)’ Diabetes Obes Metab. 2018; 20: 2840– 2851. doi:

View study


Background: A key recent study performed by Oxford University and Dr Clare Bailey looking at the feasibility of using an 800 calorie, low-carb, Mediterranean-style diet as a treatment for people with type 2 diabetes.

Results: After 8 weeks in the rapid weight loss group, average weight loss was 9.5kg, sustained over the course of the trial. Results also included a significant drop in blood sugars, blood pressure and the use of medication (none of which improved in the controlled group, who were following a standard diet). There were no significant side effects.

Find out more: Morris, E, Aveyard, P, Dyson, P, et al. (2017). A food‐based, low‐energy, low‐carbohydrate diet for people with type 2 diabetes in primary care: A randomized controlled feasibility trial. Diabetes Obes Metab. 22: 512– 520.

View study

Intermittent Fasting

Fasting-Mimicking Diet (FMD)

Background: Another major study, this time looking at the effect on various health markers of a very low calorie diet (700-1000 kcal/day) for 5 days every month for 3 months.

Results: The three cycles of FMD reduced body weight, trunk and total body fat, blood pressure and IGF-1 in comparison to a normal diet. These results were especially pronounced in the most ‘at risk’ portions of the trial groups.

Find out more: Wei, M., Brandhorst, S., Shelehchi, M., et al. (2017). Fasting-mimicking diet and markers/risk factors for aging, diabetes, cancer and cardiovascular disease. Sci Transl Med, 9(377).

View study

Intermittent Fasting vs Conventional Dieting

Background: This study compared the effects of 3 months of Intermittent Energy and Carbohydrate Restriction (IECR) compared to conventional Daily Energy Restriction (DER). The IECR group followed a 5:2 plan with 600-650 kcal/day on fasting days.

Results: The participants on the IECR diets had lost, on average, twice as much body fat as those on the DER diet. Participants on the IECR diets also had significantly greater reductions in insulin resistance than those on the DER diet.

Find out more: Harvie, M., Wright, C., Pegington, M., et al. (2013). The effect of intermittent energy and carbohydrate restriction v. daily energy restriction on weight loss and metabolic disease risk markers in overweight women. British Journal of Nutrition, 110(8), pp. 1534-1547.

View study

Intermittent Fasting and Asthma in Overweight Subjects

Background: This study examined the effects of alternate day calorie restriction (ADCR) on various health markers for overweight patients (BMI >30) with asthma. Participants spent 8 weeks eating normally every other day and eating 20% of their usual calorie consumption on the intervening days.

Results: Participants who stuck to the diet lost 8% of their initial body weight on average during the 8 weeks. Subjects’ asthma-related symptoms, control, peak expiratory flow (PEF) and quality of life (QoL) significantly improved. Results showed that an ADCR diet can have rapid and sustained beneficial effects.

Find out more: Johnson, J. B., W. Summer, R. G. Cutler, B. Martin, D. H. Hyun, V. D. Dixit, M. Pearson, M. Nassar, S. Maudsley, O. Carlson, S. John, D. R. Laub and M. P. Mattson (2007) Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radic Biol Med, 42(5), pp. 665-674.

View study

Mediterranean Diet


Background:  This was a very large trial involving 7447 individuals, who were at high risk of cardiovascular disease. Participants were randomised to a med diet supplemented with either nuts or extra virgin olive oil, or to a low-fat control group. The effects of the diet after more than 5 years observation were then investigated.

Results: A large number of papers have been published on this trial, and so the key results from each will be summarised very briefly here.

  1. A Mediterranean diet was shown to reduce the risk of a major cardiac event by 30% in the trial cohort.
  2. The Med + nuts diet was associated with a 13.7% reduction in prevalence of metabolic syndrome.
  3. Oxidised cholesterol levels, along with several other heart disease risk factors, reduced significantly in the groups on the Mediterranean diet.
  4. The Mediterranean diet reduced the risk of developing type 2 diabetes by 52%.
  5. The Mediterranean diet had beneficial effects on various cardiovascular risk factors including blood sugar levels and blood pressure.

Find out more: Estruch, R., Ros, E., Salas-Salvadó, J., et al. (2013) Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts. N Eng J Med, 378, e34.

View study

Salas-Salvadó, J., Fernández-Ballart, J., Ros, E., et al (2008) Effect of a Mediterranean Diet Supplemented With Nuts on Metabolic Syndrome Status: One-Year Results of the PREDIMED Randomized Trial. Arch Intern Med, 168(22), pp. 2449-2458.

View study

Fitó, M., Guxens, M., Corella, D., et al. (2007) Effect of a traditional Mediterranean diet on lipoprotein oxidation: a randomized controlled trial. Arch Intern Med, 167(11), pp. 1195-1203.

View study

Sala-Slavadó, J., Bulló, M., Martínez-González, MÁ (2011) Reduction in the incidence of type 2 diabetes with the Mediterranean diet: results of the PREDIMED-Reus nutrition intervention randomized trial. Diabetes Care, 34(1), pp. 14-19.

View study

Estruch, R., Martínez-González, MÁ., Corella, D., et al (2006) Effects of a Mediterranean-style diet on cardiovascular risk factors: a randomized trial. Ann Intern Med, 145(1), pp. 1-11.

View study

Adherence to Mediterranean diet and health status: meta-analysis

Background: This meta-analysis, conducted in 2008 by the University of Florence, reviewed the findings of 12 studies, together following 1.5m people.

Results: It found that those following a Mediterranean diet were 9% less likely to die young, and also less likely overall to die of heart disease, stroke or cancer. They were also less likely to develop Parkinson’s disease or Alzheimer’s.

Find out more: Sofi F., Cesari F., et al. (2008), ‘Adherence to Mediterranean diet and health status: meta-analysis’ BMJ 2008; 337:a1344, doi

View study

Subscribe to our Newsletter

Sign up to our Newsletter

    Your Cart
    Your cart is emptyReturn to Shop