Guest Blogger: Helen Bond, BSc (HONS), RD, MBDA
Helen is a Registered Dietitian and spokesperson for the British Dietetic Association with 26 years experience in food, diet, and its’ relationship to health. Passionate about communicating the role of good nutrition towards positive health and well-being, she runs her own successful dietetic practice in Derbyshire, where she provides consultancy for food companies and regularly writes and provide expert comment on nutrition news stories for magazines and national newspapers.
Which weight loss diets – fad or otherwise – are we likely to be seeing more of in future, and how do they stack up? Registered Dietitian Helen Bond investigates…
With around two thirds of adults classified as living with overweight or obesity , it’s unsurprising that many people are hoping for a magic solution to shed those unwanted pounds. Statistics show that around 1.4 million Google searches for ‘how to lose weight fast’ were made during 2021, which is equivalent to three searches per minute . But, as every health professional knows, losing weight, and especially keeping it off, has no easy shortcuts. With diet fever tending to peak in the early weeks of January, here’s which diets are likely to be popular in 2023, and how to help manage your patients’ expectations of them.
VERY LOW-CALORIE DIETS (VLCDs)
Diets with 800 calories per day or less were out of fashion for a while but they’re back with a vengeance. Modern versions of the VLCD include Michael Mosley’s Very Fast 800 diet , while VLCDs in the form of meal replacement shakes, bars, and soups (e.g., Lighter Life, Shake that Weight, Counterweight, Cambridge Weight Plan) have a wealth of new flavours and products, looking set to continue being popular through 2023.
Counterweight is a behaviour change programme widely used by the NHS with a Low Energy Diet option as a tool for initial rapid weight loss and support provided from dietitians. Visit www.counterweight.org for further information.
VLCDs have been rehabilitated by research that shows they can play an important role in medically necessary rapid weight loss, particularly for people living with obesity and morbid obesity (BMI> 30 and 40) needing to lose liver fat prior to bariatric surgery , as well as in diabetes remission . In the UK and EU, meal replacements are regulated and must provide between 200 and 400 kcal per serving, as well as a wide selection of micronutrients . For people who are want initial rapid weight loss but have poor self-control around food, VLCD total meal replacements can be helpful to circumvent the temptation of being around food.
Total meal replacements fail to equip slimmers with the skills required to successfully negotiate healthy eating and returning to “normal” food can be difficult. It can also be difficult to manage hunger on 800 or fewer calories per day, and navigate possible side effects such as dizziness, irritability, poor concentration and headaches. Plus, some meal replacement shakes use sugar alcohols (polyols) as a sweetener, which can trigger Irritable Bowel Syndrome (IBS) symptoms in some gut sensitive people. People who prepare their own VLCDs will find it very hard to achieve adequate intake of essential nutrients, such as calcium and iron.
The bottom line:
- Unless there is a pressing health reason for a VLCD, a more moderate daily calorie restriction is easier and holds the most potential for lasting weight loss .
- VLCDs shouldn’t be used for more than three weeks without medical/dietetic advice, and for a maximum of 12 weeks in total.
- VLCDs have the potential to interfere with individual’s metabolic rate. 
- Meal replacements are likely the safest VLCDs, as they must be nutritionally balanced.
- Meal replacements do not replicate all of the goodness – the variety and combination of phytonutrients found in whole foods.
Microbiome testing kits give a breakdown of your gut microbes and use that information to develop dietary recommendations that allegedly help you reach a healthy weight more easily. Zoe  has 200,000 on the waitlist of interested participants and combines microbiome analysis with personalised blood fat, and blood sugar responses to test muffins. Participants end up with a list of high-scoring foods that supposedly feed their good gut bacteria and optimise their glucose responses to food.
Does weight have more to do with the gut than we initially thought? Zoe has some weight behind it, as it feeds accumulated data from PREDICT — the world’s largest on-going nutritional study — into machine learning models to help constantly refine expected physiological responses from food, based on gut bacteria composition. The personal feedback from having your microbiome tested is also highly motivating.
While the emerging science is fascinating, we don’t yet know how relevant the microbiome/food correlations found at population level apply to specific individuals (or to put it another way, if two people have similar microbiomes, will they necessarily have the same glucose response to a specific food? We still don’t know!). The main advice you’ll get from Zoe is to eat a wide variety of fibre-rich plant foods to make your gut bugs happy — and you don’t need expensive microbiome testing to tell you that.
The bottom line:
- While the science is rapidly progressing, understanding how changes in our microbiome affects our weight is far from fully understood.
- Patients can improve their gut microbiome without having it tested — a balanced and varied diet brimming full of 30 or more different plant foods every week (such as fruits and vegetables, nuts, seeds, pulses, grains, herbs and spices) is key to this. 
Can an analysis of your DNA inform which diet is best for you? That’s the premise behind a new crop of internet sites like easydna.co.uk and nutrigenomix.com that analyse your genes from a simple cheek swab. Among other things, your DNA report will tell you if you have “fat” genes, as well as your sensitivity to carbs and ability to metabolise fats.
Some people might want to know if they have a gene that makes them hungrier, while knowing if you have a genetic variant for coeliac disease or are a slow/fast metaboliser of alcohol or caffeine is useful. But beyond that, any weight loss success is more likely to resu
lt from the considerable financial and emotional investment people make when they have DNA analysis.
For now, the science of nutrigenomics is generally still too unsophisticated to be used for truly customisable weight-loss plans . Results from the DIETFITS study also found that people who dieted according to their DNA results didn’t shed any more pounds than those who were not DNA tested .
The bottom line:
- Most DNA plans are super expensive and don’t provide too many practical action points.
- If patients do get a DNA test, it’s important that they enlist the support of a dietetic professional or qualified nutritionist to interpret the results and apply to their diet.
METABOLISM HACKING DIETS
High tech ‘metabolism hacking’ diets medicalise weight loss by monitoring fuel utilisation or glucose responses. For example Lumen uses home carbon dioxide breath monitoring to determine whether you are burning fat or carb as fuel, while US start-ups Levels , Nutrisense  and January , use continuous glucose monitoring (CGM) to guide food choices. It’s likely that these or similar diets will start making their way here during 2023.
Glucose monitoring has the potential to be useful for people with insulin resistance or diabetes. It can discourage over consumption of ultra-processed foods and highlights the link between physical activity and more nimble metabolic response, potentially encouraging better exercise habits.
Again, these come with a hefty price tag, and wearing a glucose monitor is invasive and may promote health anxieties. Most metabolism-hacking diets subscribe to the carbohydrate-insulin model of obesity, which is over simplistic and overlooks that weight gain only occurs when calories in general (not just carbohydrate) are over consumed.
The bottom line:
- Patients are better off putting their monthly subscription cost into purchasing more healthy, nutritious whole foods.
APP BASED BEHAVIOURAL CHANGE DIETS
Increasingly popular psychology-based apps like Noom  and Second Nature  encourage people wanting to lose weight to think about food and fitness differently. Users get sent mini lessons in psychology and behavioural change and most apps put people in touch with a coach who checks your progress and sends motivational messages.
The psychological approach to dieting has good results. Second Nature is one of the few lifestyle change companies that received backing from the NHS with a BMJ study  suggesting the program resulted in twice as much weight loss after 12 months than 4 other programmes. Meanwhile, Noom research  suggests 78% of people lost weight while using the Noom app for an average of 9 months, with 23% losing more than 10% of their body weight.
Being app based may not suit older users who aren’t as comfortable using smartphones. And some people say they find the motivational messaging a little trite and/or condescending. You’re encouraged to cook meals from scratch, which might not work for very busy people.
The bottom line:
- Behavioural change apps have some good evidence behind them and are another tool for some people who really struggle with weight loss.
MEAL KIT DIETS
Meal delivery services boomed during the pandemic and are still increasing in popularity. New options pop up all the time and every sort of eating requirement can be catered for. Companies that cater with weight loss in mind include The Good Prep, Hello Fresh and Balance Box. Meals can either be pre-prepared (just re-heat) or sent as ingredients to compile into a recipe.
Most meal prep companies employ registered dietitians or qualified nutritionists, and create well-balanced meals, so if patients have the budget for them, they can be a healthy and effective way to manage weight. Having portion-controlled meals delivered allows users to avoid unwise supermarket decisions and to keep unnecessary food temptations out of the house.
Meal kits don’t really work for families, and there’s not much flexibility for adjusting intakes for days when people are very active or expending more calories. Pre-prepped meals that you just heat in the microwave don’t encourage the development of cooking skills, and cook-chill meals may be less nutritious due to a decline in vitamin levels .
The bottom line:
- Helpful option for some individuals and couples to manage their weight, though costly.
- Meals made from raw ingredients may be more nutritious than pre-prepped versions.
KETO / INTERMITTENT FASTING COMBINATION DIETS
Why follow just one latest diet craze when you can follow two? The keto diet and intermittent fasting (IF) have both been very popular in recent years and showsno sign of slowing down with lots of Keto products widely available online and in the supermarket – and now there’s a significant trend for the two to be combined. For example, the Eat Like a Bear diet  advocates people eat a Keto diet (very low carb (5-10%), high fat (70-80%) while doing 16/8 style fasting (eating only during an 8-hour window every day).
For people who are determined to stay in ketosis, IF may help the body reach this state, and maintain it easier than doing the keto diet alone. Some reviews of IF suggest it may have positive outcomes in terms of health improvements, such as improve glucose regulation, increase stress resistance, and suppress inflammation  – although, as always, more long-term robust human studies are needed and to figure out what ‘window of eating’ is the most beneficial for health. Plus, there appears to be no evidence that IF diets lead to disordered eating.
Although researchers are continuing to investigate the use of the keto diet in glucose management in type 2 diabetes, obesity and other medical conditions, it has only been used clinically to treat epilepsy (not for the everyday dieter) and as such, there’s still very little known about its safety and effectiveness for weight loss in the long term – partly because it’s so difficult to maintain. A 2021 review suggested that downsides could include high LDL cholesterol, increased risk of cancer and kidney stones . IF is also potentially unsuitable for people with diabetes – especially in patients on insulin therapies, due to the risk of hypoglycaemia.
The bottom line:
- Using Keto and IF together is an untrusted method of weight loss with potential for adverse effects on health.
- If patients still wish to follow the diet – rather than dismiss it outright, highlight the lack of clinical evidence and suggest an alternative weight loss method like the 5:2 diet and Alternate Day Fasting (ADF) where most of the research has been conducted.
With more of us starting to engage with environmental issues, the focus on plant-based diets is growing by the day, and so it should be! However, a zero-tolerance approach to meat and dairy is very last year! For 2023, expect more “reducetarianism” (also known as flexitarianism), which involves significantly reducing, but not necessarily eliminating, animal products to improve health and protect the environment and animal welfare (www.reducetarian.org). Instead, focusing on better quality e.g. grass fed, free-range meat, cell-cultured eggs and sustainably sourced seafood.
This is one nutritional trend that it’s easy to get fully on board with because it ticks all the boxes for good nutrition and eco-friendliness, while also being achievable. Diets that aren’t meat heavy bring health benefits that include reduced risk of heart disease and diabetes , while plant-based foods like vegetables, grains and soy tend to have a low energy density, helping people to feel fuller on fewer calories – which is good news for patients wanting to whittle down their waistlines.
Very few! Some plant-based diets can be low in calcium, but shortages of this nutrient can be prevented by ensuring dairy alternatives are calcium fortified. Reducetarian diets can also increase the risk of anaemia, if iron-rich sources aren’t included. Patients should be encouraged to consume iron sources such as nuts, pulses, whole grains and leafy greens, alongside vitamin C sources to improve absorption of the mineral. Occasional intake of red meat, dairy, eggs and oily fish will also help to bump up patients’ iron, iodine, vitamin D and omega-3 intake, too.
The bottom Line:
- Reducetarianism is a healthy and sustainable way to eat, and in turn, could assist weight loss.
- Try to get patients to ease into being reducetarian – for example, by going meatless one day a week or switching out full fat cows milk in tea and coffee for a lower fat and sugar plant-based drink alternative.
Moving forward in 2023…
So, what has the past year taught us or brought to mind? The evidence base added to in 2022 highlights obesity is a complex condition with genetic, biological, psychological and environmental factors all playing a part. As dietitians and other health professionals working in the field of obesity know, there is no ‘one size fits all’ for helping people to lose weight and no single solution to obesity. Everyone is different and any weight loss plan needs to be tailored to the individual. It’s about helping patients find a way of eating that they can enjoy and stick to in the long term – not just a ‘quick fix’ diet or ‘magic solution’ based on pseudoscience and little evidence, they’ll inevitably give up on. There’s a lot of conflicting advice out there about what we should and shouldn’t eat to look after our weight and improve our health, so it’s easy to understand how patients may become misled and confused. With diet trends likely to continue to be a big feature in 2023, it’s our role as health professionals, to cut though the confusion and support people on their journey to achieve a healthier weight – whether that’s by intermittent fasting, a vegan, vegetarian or reducetarian diet or a version of the Mediterranean or DASH diet – whatever style of healthy eating that’s right for that person.
- Health Survey For England 2019. Adults’ Health. NHS Digital. Available at: https://digital.nhs.uk/data-and-information/publications/statistical/health-survey-for-england/2019/main-findings Accessed October 2022.
- Michael Mosley’s Very Fast Diet. Available atVery Fast 800 diet Accessed October 2022.
- Weight Loss Statistics 2021 – Facts and Figures in the UK. Pharmacy Direct GB.
- Holderbaum M, Casagrande DS, Sussenbach S, Buss C. Effects of very low calorie diets on liver size and weight loss in the preoperative period of bariatric surgery: a systematic review, Surgery for Obesity and Related Diseases. Volume 14, Issue 2,2018: 237-244.
- Lean MEJ, Leslie W, Barnes A, Brosnahan N, Thom G, McCombie L et al. Durability of a primary care-led weight-management intervention for remission of type 2 diabetes: 2-year results of the DiRECT open-label, cluster-randomised trial. The Lancet Diabetes & Endocrinology. Volume 7, Issue 5, 2019: 344-355.
- The European Parliament and the Council of the European Union. Commission Directive 96/8/EC of 26 February 1996 on foods intended for use in energy-restricted diets for weight reduction. Official Journal of the European Union. 2007.
- Franz et al (2007). Weight-loss outcomes: a systematic review and meta-analysis of weight-loss clinical trials with a minimum one-year follow-up. Available at https://pubmed.ncbi.nlm.nih.gov/17904936/ Accessed October 2022.
- Muller et al. Changes in Energy Expenditure with Weight Gain and Weight Loss in Humans. Current Obesity Reports, 2016 (4) 413-423. Available at ncbi.nlm.nih.gov/pubmed/27739007 Accessed October 2022
- Available at https://joinzoe.com/ Accessed October 2022.
- McDonald D, Hyde E, Debelius JW, et al. American Gut: an Open Platform for Citizen Science Microbiome Research. mSystems. 2018; Vol.3 (3).
- The basics. The Nutrition Society. Available at https://www.nutritionsociety.org/blog/nutrigenomics-basics Accessed October 2022.
- Gardner CD, Trepanowski JF, Del Gobbo LC, et al. Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial. 2018;319(7):667–679. doi:10.1001/jama.2018.0245
- Available at www.levelshealth.com Accessed October 2022.
- Nutri Sense. Available at nutrisense.io Accessed October 2022.
- Available at www.january.ai Accessed October 2022.
- Available at www.noon.com. Accessed October 2022.
- Second Nature. Available at secondnature.io Accessed October 2022.
- Ross JAD et al. Uptake and impact of the English National Health Service digital diabetes prevention programme: observational study. BMJ Open Diabetes Res Care. 2022 May; 10 (3):e002736.
- Chin SO, Keum C, Woo J, Park J, Choi HJ, Woo JT, Rhee SY. Successful weight reduction and maintenance by using a smartphone application in those with overweight and obesity. Sci Rep. 2016 Nov 7; (6):34563.
- Williams P. Vitamin Retention in Cook/Chill and Cook/Hot-Hold Hospital Foodservices. Journal of the Academy of Nutrition and Dietetics. 1996; Vol 96, Issue 5, P490-498.
- Eat Like a Bear! Available at eatlikeabear.com Accessed October 2022.
- Rafael de Cabo, Mark P. Mattson. Effects of Intermittent Fasting on Health, Aging, and Disease. The New England Journal of Medicine. Available at https://www.nejm.org/doi/full/10.1056/NEJMra1905136 Accessed October 2022.
- Crosby L et al. Ketogenic Diets and Chronic Disease: Weighing the Benefits Against the Risks. Frontiers in Nutrition, 16 July 2021. Available at https://doi.org/10.3389/fnut.2021.702802 Accessed October 2022.
- Micha R et al. Association Between Dietary Factors and Mortality From Heart Disease, Stroke, and Type 2 Diabetes in the United States. JAMA.2017; 317(9):912–924. doi:10.1001/jama.2017.0947
- Fad diets: Food Fact Sheet. Available at www.bda.uk.com. Accessed October 2022.
RELATED MYNUTRIWEB CONTENT
Addressing Weight Stigma in Healthcare (2022). Roundtable with Dr Giles Yeo on the issue of weight stigma
Thank you for this really helpful summary, much appreciated.