Eating fat and cutting carbs

CEBM response to “Eat Fat, Cut The Carbs and Avoid Snacking to Reverse Obesity and Type 2 Diabetes”

Initiatives to provide trustworthy evidence-based dietary and nutrition information to patients and clinicians about type 2 diabetes and obesity should be welcome. However the report, released by the National Obesity Forum (NOF) in collaboration with the newly formed “Public Health Collaboration”, appears to be highly unsystematic in its approach to the recommendations it makes and will likely add to the confusion and misinformation provided to practitioners, patients and members of the general public.

Based on the methods used in generating this report there are a number of reasons why the reliability and robustness of its recommendations should be questioned:

  • A number of statements put forward in the report appear to contradict available statements from the National Obesity Forum’s website. The report’s recommendation to “dissociate physical activity from obesity” contradicts the information that the NOF provide for health care professionals. For example, the ”Obesity Care Pathway Toolkit”, currently available from the NOF website, includes statements such as  Physical activity plays an important part in the prevention and management of obesity, but only if it is sustainable” and “Clients who increase their physical activity maintain their weight loss for longer”. Furthermore, this new report claims “Eating Fat Does Not Make You Fat”. However, the ”Obesity Care Pathway Toolkit” for health professionals includes advice to “choose foods that have no more than 3 – 5 grams of fat per 100 grams of product”. Such contrasting statements provide little confidence in recommending the NOF website as a reliable and consistent source of information for healthcare professionals and patients.
  • The report states that “evidence based nutrition should be incorporated into education curricula for all healthcare professionals”. This is laudable. However, a desire to incorporate the best available evidence into both a learning environment and clinical practice should recognise the value that systematic reviews have in reducing uncertainty. However, the majority of references that underpin the report appear to arise from editorials, non-systematic narrative reviews and single studies; only 5 of the 43 references cited in the report, are in the form of a systematic review. Furthermore, there is no mention of whether any of the included references were found using a systematic search, therefore increasing the risk of including only “cherry picked” citations and the subsequent introduction of a biased view.
  • The report omits key systematic review evidence that would challenge some of the statements made within it. For example, the report makes a request to “dissociate physical activity from obesity” yet ignores a systematic review of randomised controlled trials that demonstrated that combined diet and exercise behavioural weight management programs were associated with greater longer term weight loss than diet alone. The findings from this systematic review were consistent with the results from a previous Cochrane systematic review, also not cited in this report, which supports physical activity when combined with dietary advice for weight loss.
  • The report lends itself heavily to the promotion of a low carbohydrate, high fat diet. It is therefore surprising that another recent and highly relevant systematic review and meta-analysis comparing low fat diets to low carbohydrate diets is referred to but not cited in their report. This review demonstrated that the average difference in weight loss, after at least 1 year, between a low fat and low carbohydrate diet was approximately 1·15 kg in studies where weight loss was the goal. In studies where weight loss was not the goal (pertinent to population advice for the prevention of weight gain), the review found no significant differences in weight change between the diets. Relatively small, or no differences in weight change from empirical evidence of low carbohydrate diets, do not seem to justify some of the overarching statements made in this report.
  • The same analysis also found that when [albeit heterogeneous] studies of low fat diets were compared to usual diets, the low fat diets resulted in an average weight loss of 5·41 kg more than a usual diet. This finding conflicts with some of the overarching advice contained within this report in relation to the potential benefits of low fat diets.
  • Recommendations derived from controlled research studies should also try to consider and reflect upon the wider context to minimise the risk of unintended consequences.  This report makes no reference to a systematic review of observational studies, which found low carbohydrate diets to be associated with a higher risk of mortality.
  • A set of recommendations, such as those being made in this report, should also make an attempt to assess the quality or uncertainty of the data used as evidence to support their views or recommendations. Any limitations on being able to apply evidence should be discussed in an open and transparent way. However, the authors of this report make no such attempt to do this.
  • The NOF, an independent professional organisation, recognises on their website (as of the time this response was written) the support, both professional and financial, of other organisations. These are stated as including the Department of Health as well as the National Institute of Clinical Excellence. However, the statements within the report appear to suggest a paradigm shift in nutrition advice away from current recommendations e.g. from the Department of Health and NICE guidance CG189. Other professional and financial partners of the NOF (past and present) are listed as including commercial weight loss companies such as LighterLife UK Limited, Slim Fast Foods Ltd and Rosemary Conley Enterprises. It is unclear whether statements within this report such as “Stop counting calories” and “We must dissociate physical activity from obesity” are statements supported by the partners of the NOF as well. Taken together, the report projects a confusing picture for service users on where they can and should seek reliable advice and support.

The impact of obesity and type 2 diabetes, on both the individual and society, remains considerable, arguably one of the largest public health problems of the current era. Effective measures to prevent and reduce the burden of ill health should seek to be patient focused, include the best available and most up to date evidence and wherever possible be consistent.  Unfortunately dietary and nutritional advice is one of the most contentious, misunderstood and misreported areas of public health. Polarised views and “expert” opinions further inflate these problems. A report of this nature, from professional groups, carries particular responsibility to adopt a systematic, rigorous and transparent approach if it is to help and not hinder improvements in diet and reduce the burden of preventable diseases.


Authors of statement

Dr David Nunan  Departmental Lecturer in Evidence Based Medicine

Dr Kamal R. Mahtani – GP and Deputy Director

Centre for Evidence Based Medicine, Nuffield Department of Primary Care Health Sciences, University of Oxford.

This response will be posted on and a PDF of this statement can be downloaded here.


Dr David Nunan and Dr Kamal R. Mahtani are both members of the Royal College of General Practitioners (RCGP) steering committee to support the new Physical Activity and Lifestyle clinical priority.

Both Dr Nunan and Dr Mahtani have received funding for research from the NHS National Institute for Health Research School for Primary Care Research (NIHR SPCR) and the RCGP for independent research projects related to physical activity and dietary interventions. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, the RCGP or the Department of Health.

They declare no other relevant conflicts of interest.


Related news

Wednesday 8 June 2016 The National Obesity Forum (NOF) has no plans to replace the four members who resigned last week – after a controversial pro-fat report was released by mistake – according to the organisation

Friday 3 June 2016 National Obesity Forum board members resign over controversial report on fat intake – International Business Times

Friday 3 June 2016 Anti-obesity campaigners resign over low-fat diet report – The Guardian

Friday 3 June 2016 Statement from the National Obesity Forum

Tuesday 31 May 2016 Should you really eat fat to stay slim? The new food rules explained – The Telegraph

Sunday 29 May 2016 National Obesity Forum faces backlash over ‘extremely dangerous’ diet advice – The Independent

Saturday 28 May 2016 National Obesity Forum faces backlash over ‘dangerous’ diet advice – The Guardian

Monday 23 May 2016 Report attacks official guidance on low-fat diets – NHS Choices 

Monday 23 May 2016 Between a rock and a lard place – is fat good for us, or what? – The Guardian

Monday 23 May 2016 Public Health England: Advice to eat more fat ‘irresponsible’ BBC news

Monday 23 May 2016 Official advice on low-fat diet and cholesterol is wrong, says health charity – The Guardian

Sunday 22 May 2016 Expert reaction to new report on diet as published by the National Obesity Forum – Science Media Centre