Fad diets

There are lots of reasons for wanting to lose weight or change our diet. However, this should not be at a cost either to your health, your relationship with food or your wallet.

Tempting though the endless range of ‘quick-fix’ and ‘miracle’ options may be, the promises they make for rapid weight loss for minimum effort are often unrealistic and unsustainable. 

Unfortunately, there is no magic solution to weight loss that lasts. There is no such thing as a ‘magic diet’. Most fad diets are associated with some degree of nutritional or health risk. A fad diet is offering a short-term solution to a long-term problem.

fad diet fad diets smoothie

What is a fad diet?

A fad diet is a plan that promotes results such as fast weight loss without robust scientific evidence to support its claims. Popular ones include plans where you eat a very restrictive diet with few foods or an unusual combination of foods. They may only allow you to eat certain foods at certain times. Fad diets often consist of expensive and unnecessary food products, ingredients and/or supplements.

Where’s the harm?

Many fad diets will lead to initial weight loss but this weight loss is often lean muscle and fluid loss instead of body fat. Often these diets cannot be followed long term as many people become fed up with the rigid rules and limits. 

When food groups are demonised, and internal cues around hunger and fullness ignored, this can lead to cycles of weight loss followed by weight regain. This cycle can affect our relationship with food, leading to feelings of failure rather than developing the skills and confidence to manage diet and weight in a healthy manner.

How to tell the diet fact from the fiction?

Beware! Stay away from diets that: 

  • promise a magic bullet to lose weight without having to change your lifestyle in any way. These include diet pills, lotions, wearables such as sweat suits 
  • promise rapid weight loss of more than 1kg (2lbs) of body fat a week such as keto or extreme or total fasting
  • recommend magical fat-burning effects of foods such as the grapefruit diet or hidden ingredients in foods (caffeine/coffee diet) or alleged fat burning substances such as green tea extract or raspberry ketones
  • promote the avoidance or severe limitation of a whole food group such as dairy products, all carbohydrates, or a staple food such as wheat. Examples include very low carb/keto (<50g carbohydrate per day unless medically prescribed), carnivore diets or paleo diets
  • suggest substituting everyday foods or food groups for expensive doses of supplements (e.g. IV vitamin drips), expensive ingredients, or special products such as the bulletproof diet or weight loss injections
  • promote eating mainly one type of food (mono diet) e.g. cabbage soup diet, chocolate diet or boiled eggs diet, or avoiding all cooked foods (raw food diet)
  • recommend eating foods only in particular combinations based on your genetic type or blood group (blood group diet)
  • suggest that you are living with overweight because of a food allergy or a yeast infection
  • recommend 'detoxing' or avoiding foods in certain combinations such as fruit with meals
  • are based on claims that we can survive without food or having liquid meals only e.g. water fasting or juice cleanses
  • offer no supporting evidence apart from personal success stories 
  • focus only on your appearance rather than on health benefits with rigid rules
  • are selling you products or supplements
  • recommend eating non-food items such as cotton wool or hydrochloric acid
  • have recommendations based on a single study, testimonials or unrealistic amounts of a food e.g. chilli 
  • recommend the same diet for everyone without accounting for specific needs
  • are based on a ‘secret’ that doctors are yet to discover or ‘don’t want you to know’
  • imply that food can change body chemistry
  • misinterpret medical tests or how the body works such as the alkaline diet, collagen diet
  • are labelled as ‘wellness’ but really are about strictly controlling food e.g. clean eating

Remember, if it sounds too good to be true – it probably is!

Who knows what?

Social media, filters and photoshopped images will have us believe that famous celebrities are picture perfect all the time. However, this is unrealistic and can make us feel bad about ourselves and our own ‘imperfections’. Just because someone is famous does not make them an expert in nutrition.

Many people claim to be experts in nutrition yet have limited knowledge and offer no protection to the public. You should be wary of unqualified practitioners who may be offering unproven techniques to diagnose and treat nutritional problems including:

  • iridology
  • kinesiology
  • craniosacral therapy
  • hair mineral analysis
  • face reading
  • tongue reading
  • colonic irrigation
  • magnetic therapy

Dietitians have recognised qualifications and are regulated. They will be able to guide you through the maze of dietary information that surrounds us and give you safe, unbiased, evidence-based advice. Ask your doctor to refer you to a dietitian or find a freelance dietitian.


  • Fad diets can be tempting as they promise a quick fix to a long-term problem. But restrictive, or extreme diets that have no scientific basis can put your health at risk. 
  • Following a fad diet may cause a cycle of weight loss followed by weight gain.
  • Dietitians will be able to help you know if dietary information is safe and based on evidence.
  • The best way to maintain a healthy weight is to consider your diet as a whole.
  • Make healthier choices where possible and include variety and balance.
  • Listen to your body's hunger and fullness cues.
  • Be aware of portion sizes and consider activity levels.


Alhassan S et al (2008) Dietary adherence and weight loss success among overweight women: results from the A TO Z weight loss study. Int J Obes.; 32(6):985-91.

Andersen JW et al (1999) Long-term weight maintenance after an intensive weight-loss programme. J Am Coll Nutr. 1999;18 [6]: 20-7

Ashley JM, St Jeor ST, Schrage JP et al (2001) Weight control in the physicians office. Arch Intern Med;161:1599-1604.

Aston LM, Stokes CS, Jebb SA (2008) No effect of a diet with a reduced glycaemic index on satiety, energy intake and body weight in overweight and obese women. Int J Obes.; 32(1): 160–165.

Buchholz AC & Schoeller DA (2004) Is a calorie a calorie? Am J Clin Nutr; 79 (suppl): 899S–906S.

Clifton PM et al (2008) Long-term effects of a high-protein weight-loss diet. Am J Clin Nutr.;87(1):23-9.

Dansinger ML et al (2005) Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction: a randomized trial. JAMA; 293(1): 43-53.

Dansinger M et al (2007) Meta-analysis: The Effect of Dietary Counseling for Weight Loss. Ann Intern Med; 147: 41-50.

Das SK et al (2007) Long-term effects of 2 energy-restricted diets differing in glycemic load on dietary adherence, body composition, and metabolism in CALERIE: a 1-y randomized controlled trial. Am J Clin Nutr.; 85(4):1023-30.

Dietitians in Obesity Management UK, position statements  - meal replacements, VLEDs, low carbohydrate diets. http://domuk.org/category/professional-matters/position-statements/

Ebbeling CB et al (2012).  Effects of Dietary Composition on Energy Expenditure During Weight-Loss Maintenance. JAMA. 307(24):2627-2634.     doi:10.1001/jama.2012.6607

Flechtner-Mors M, Ditschuneit H H, Johnson T D et al (2000) Metabolic and Weight Loss Effects of a Long-Term Dietary Intervention in Obese Patients: Four-Year Results. Obes Res; 8: 399-402.

Foresight (2007) Tackling obesities: Future choices. www.foresight.gov.uk/OurWork/ActiveProjects/Obesity/Obesity

Foreyt JP et al (2009). Weight-reducing diets: Are there any differences?  Nutr Rev;  67(Suppl.1): S99–S101

Foster GD et al (2003) A randomized trial of a low-carbohydrate diet for obesity. N Engl J Med 2003; 22; 348 (21):2082-90.

Foster GD et al (2010) Weight and Metabolic Outcomes After  2 Years on a Low-Carbohydrate Versus Low-Fat Diet A Randomized Trial. Ann Intern Med; 153 (3): 147-157

Fuglestad PT, Jeffery RW, Sherwood NE (2012). Lifestyle patterns associated with diet, physical activity, body mass index and amount of recent weight loss in a sample of successful weight losers.Int J Behav Nutr Phys Act. 9 (1):79.

Goff SL et al (2006) Nutrition and weight loss information in a popular diet book: is it fact, fiction, or something in between? J Gen Intern Med.;21(7):769-71.

Golay A et al. Similar weight loss with low-energy food combining or balanced diets. International Journal of Obesity & Related Metabolic Disorders 2000; 24 (4): 492-6.

Hall KD et al (2011). Quantification of the effect of energy imbalance on bodyweight.  Lancet 378 (9793): 826-837.

Harvie MN et al (2010). The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. Int J Obes; 35(5), 714–727.

Harvie 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. Br J Nutr ;1-14.

Heshka S, Anderson JW, Atkinson RL et al (2003) Weight loss with self-help compared with a structured commercial program: a randomized trial. JAMA.; 289 (14):1792-8.

Karhunen L et al (2012) Psychobehavioural factors are more strongly associated with successful weight management than predetermined satiety effect or other characteristics of diet. J Obes. 2012:274068.

Johnston, B. C., Kanters, S., Bandayrel, K., Wu, P., Naji, F., Siemieniuk, R. A., Ball, G. D., Busse, J. W., Thorlund, K., Guyatt, G., Jansen, J. P., & Mills, E. J. (2014). Comparison of weight loss among named diet programs in overweight and obese adults: a meta-analysis. JAMA, 312(9), 923–933. https://doi.org/10.1001/jama.2014.10397

Lavin J et al (2006) Feasibility and benefits of implementing a Slimming on Referral service in primary care using a commercial weight management partner. Public Health; 120 (9):872-81.

Malik, N., Tonstad, S., Paalani, M., Dos Santos, H., & Luiz do Prado, W. (2020). Are long-term FAD diets restricting micronutrient intake? A randomized controlled trial. Food science & nutrition, 8(11), 6047–6060. https://doi.org/10.1002/fsn3.1895

Mann et al. (2007) Medicare's search for effective obesity treatments: diets are not the answer. Am Psychol 2007;62:220–33

National Task Force on the Prevention and Treatment of Obesity (2000) Dieting and the development of eating disorders in overweight and obese adults. Arch Intern Med. 160 (17):2581-9.

National Weight Control Registry research findings. www.nwcr.ws/Research


Norris SL et al (2005) Long term non-pharmacological weight loss interventions for adults with type 2 diabetes mellitus. Cochrane Database of Systematic reviews, Issue2. Art No.:CD004095. DOI: 10.1002/14651858.CD004095.pub2

Nordmann AJ et al (2006) Effects of Low-Carbohydrate vs Low-Fat Diets on Weight Loss and Cardiovascular Risk Factors. Arch Intern Med; 166: 285-293.

Noakes M et al (2005) Effect of an energy-restricted, high-protein, low-fat diet relative to a conventional high-carbohydrate, low-fat diet on weight loss, body composition, nutritional status, and markers of cardiovascular health in obese women. Am J Clin Nutr. 81(6):1298-306

Obert, J., Pearlman, M., Obert, L., & Chapin, S. (2017). Popular Weight Loss Strategies: a Review of Four Weight Loss Techniques. Current gastroenterology reports, 19(12), 61. https://doi.org/10.1007/s11894-017-0603-8

Passos, J. A., Vasconcellos-Silva, P. R., & Santos, L. (2020). Cycles of attention to fad diets and internet search trends by Google trends. Ciclos de atenção a dietas da moda e tendências de busca na internet pelo Google trends. Ciencia & saude coletiva, 25(7), 2615–2631. https://doi.org/10.1590/1413-81232020257.23892018

Poulter J & Hunt P (2007) An evaluation of Weight Watchers referrals. Practice Nursing 18; (5), 236-241.

Rock CL et al (2007) Randomized trial of a multifaceted commercial weight loss program. Obesity; 15 (4): 939-49.

Sacks FM et al (2009). Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates. JAMA 2009; 360 (9):859-873.

Shai I & Stampfer MJ (2008) Weight-loss diets—can you keep it off? Am J Clin Nutr; 88: 1185– 6.

Sherry L. Pagoto; Bradley M. Appelhans, A Call for an End to the Diet Debates JAMA. 2013;310(7):687-688. doi:10.1001/jama.2013.8601.

Shai I et al (2008) Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. N Engl J Med. ;359(3): 229-41.

SIGN (2010). Management of Obesity. A national clinical guideline. www.sign.ac.uk

Sloth B & Astrup A (2006) Low glycemic index diets and body weight. Int J Obes. 30 Suppl 3:S47-51.

Tsai AG & Wadden TA. (2006). The Evolution of Very-Low-Calorie Diets:An Update and Meta-analysis. Obesity 14 (8): 1283-1293.

Tsai AG & Wadden TA (2005) Systematic review: an evaluation of major commercial weight loss programs in the US. Ann Intern Med.; 142(1):56-66.

Thomas DE et al (2007). Low glycaemic index or low glycaemic load diets for overweight and obesity. Cochrane Database Syst Rev. July 18 (3): CD005105.

Varady KA et al (2009). Short-term modified alternate-day fasting: a novel dietary 
strategy for weight loss and cardioprotection in obese adults. Am J Clin Nutr; 90(5):1138-1143.

Weight cycling (1994) National Task Force on the Prevention and Treatment of Obesity. JAMA; 272 (15): 1196-202.

Wing RR et al (2008) Maintaining large weight losses: The role of behavioral and psychological factors. J Consult Clin Psychol; 76 (6): 1015–1021.

Wing RR & Phelan SS (2005).  Long-term weight loss maintenance. Am J Clin Nutr. 82 (1 Suppl):222S-225S.