Adapted from BMJ 1 April 2023
Surgeon Scarlett Mc Nally writes: In the 30 and more years since I qualified, England has had 14 obesity strategies including 689 policies. In that time the prevalence of obesity has almost doubled from 15% in 1993 to 28% of the adults in the UK in 2019. This spectacular failure of policy is probably due to a misplaced focus on individual behaviours rather than social, fiscal, or regulatory policies.
High body mass index is the fourth leading risk factor for disease in the UK and a major risk factor for 13 cancers. People with obesity are 7 times more likely to develop type two diabetes, contributing to worsening health and the risk of amputations, sight loss, kidney dysfunction and complications of surgery.
Several aspects of physiology are not widely understood or applied. First, starchy carbohydrates such as bread, pasta, rice and potatoes, are rapidly converted to sugars that are preferentially stored as fat.
Release of the hormone insulin is triggered by high sugar levels, helping to store sugar as fat and leading to the post meal dip in blood sugar around two hours later. Fats, proteins and fibre cause a lower insulin spike, leaving us feeling fuller for longer. This is the basis of low carbohydrate diets.
Second, the balance of hormones means our bodies are either storing fat or using it. Any food intake reduces fat loss for some time. This is the justification for intermittent fasting routines.
Third, it takes 20 minutes to feel full after eating. Slower eating helps us to avoid overeating at meals, helps us consider portion sizes more wisely and helps us resist second helpings.
Fourth, exercise help the body to burn fat by lipolysis.
So what do we do with this knowledge? Perhaps suggesting what and when to eat is a better option than new, expensively promoted semaglutide injections, which mimic a hormone that decreases appetite.
Replacing carbohydrates means that more protein, fat, or fibre is needed. This can be difficult in a cost of living crisis, as obesity is highly related to social deprivation. A person is twice as likely to experience obesity (37%) in the most deprived areas as in the least deprived (19%).
Tackling obesity then should include social initiatives to fight deprivation such as healthy school meals.
Our environment needs to change, through improved funding and regulation. It should permit physical activity, with play parks, walkable neighbourhoods, cycle lanes, and low traffic areas.
Commercial food companies should be subject to the full weight of regulations, which should be applied to any junk food advertising. We need initiatives to improve access to affordable, high quality food, which is shamefully poor in many deprived areas.
Obesity should not be considered a “lifestyle” problem. It requires a whole community approach focused on environments, regulation, and funding.
I’m delighted that The BMJ has stood by this article and decided against retraction. Two outside reviewers judged that the criticisms of the piece did not merit its retraction, and in the end, the corrections made by The BMJ do not, in my view, materially undermine any of the article’s key claims. This article therefore stands as one of the most serious ever, peer-reviewed critiques of the expert report for the US Dietary Guidelines for Americans (DGAs).
The importance of the DGAs, and therefore of this article, should not be understated (and indeed was recognized by many in the mainstream media when the article was published). The DGAs have long been considered the “gold standard,” informing the US food supply, military rations, US government feeding assistance programs such as the National School Lunch Program which are, altogether, consumed by 1 in 4 Americans each month, as well as the guidelines of professional societies and governments around the world, and eating habits generally.
Yet rates of obesity began to shoot upwards in the very year, 1980, that the DGAs were introduced, and the diabetes epidemic began soon thereafter. A critically important yet little understood issue is why the DGAs have failed, so spectacularly, to safeguard health from the very nutrition-related diseases that they were supposed to prevent.
In documenting fundamental failures in the science behind the DGAs, this article offers new insights; It establishes that a vast amount of nutrition science funded by the National Institutes of Health and other governments worldwide has, for decades, been systematically ignored or dismissed, and that therefore, that the DGAs are not based on a comprehensive reviews of the most rigorous science. Incorporating this long-ignored relevant science would likely lead to fundamentally different DGAs and could very well be an important step in infusing them with the power to better fight the nutrition-related diseases.
A fundamental question is why 170+ researchers (including all the 2015 DGA committee members, or “DGAC”), organized by the advocacy group, the Center for Science in the Public Interest (CSPI), would sign a letter asking for retraction. After all, in the weeks following publication, any person had the opportunity to submit a “Rapid Response” to the article, and both CSPI and the DGAC did so, alleging many errors. I responded to them all in my Rapid Response. This is the normal post-publication process.
Yet after all this, CSPI returned for a second round of criticisms, recycling two of the issues (CSPI points #3 and #10) that I had already addressed in my Rapid Response (and which had required no correction), adding another 9 (one of which, #4, contained no challenge of fact), and demanding that based on these alleged errors, the article be retracted. CSPI then circulated this letter widely to colleagues and asked them to sign on.
This lack of substance in the retraction effort seems to point to the reality that it was first and foremost an act of advocacy—a heavy handed attempt to silence arguments with which CSPI, a longtime supporter of the Dietary Guidelines and its allies disagree.[ footnote 1] And this applies not just to the retraction letter but to other CSPI efforts to stifle alternative viewpoints. Earlier this year, for example, I was dis-invited from the National Food Policy Conference after CSPI, together with the USDA official in charge of the Dietary Guidelines, threatened to withdraw if I were included, details of which are reported here and which a Spiked columnist called an act of “censorship.”
It’s important to note that I am not the only person disturbed by the lack of rigorous science underpinning our dietary guidelines. Numerous scientists around the world have expressed concern about the science. And indeed, this consternation is shared by no less than the US Congress, which held a hearing on Oct 7, 2015 to address its serious doubts about the DGAs. Such was this concern that last year that Congress mandated the first-ever major peer-review of the DGAs, by the National Academy of Medicine. Congress appropriated $1 million for this review, and it additionally stipulated that all members of the 2015 DGA committee recuse themselves from the process.
What is the dangerous information challenging the DGAs that cannot be heard on a conference panel nor published in a peer-reviewed journal?
The major findings of this article are that:
1. The DGAC’s finding that the evidence of a “strong” link between saturated fats and heart disease was not clearly supported by the evidence cited. (Note that as of last year, the Heart and Stroke Foundation of Canada no longer limits saturated fats. Note, also, that Frank Hu, the Harvard epidemiologist in charge of the DGAC review on saturated fats, was an energetic promoter of the retraction letter against my article that critiqued his review, according to emails obtained through FOIA requests);
2. Successive DGA committees have for decades ignored or dismissed a large body of rigorous (randomized controlled trial) literature on the low-fat diet, on more than 50K subjects, collectively finding that this diet is ineffective for fighting obesity, diabetes, heart disease or any kind of cancer;
3. Although the DGAs have for decades recommended avoiding saturated fats and cholesterol to prevent heart disease, no DGA committee has ever directly reviewed the enormous body of rigorous (government-funded, randomized controlled trials) evidence, testing more than 25,000 people, on this hypothesis. Many reviews of this data have concluded that saturated fats have no effect on cardiovascular mortality;
4. The DGAC ignored a large body of scientific literature on low-carbohydrate diets (including several “long term” trials, of 2-years duration) demonstrating that these diets are safe and highly effective for combatting obesity, diabetes, and heart disease;
5. The Nutrition Evidence Library (NEL) set up by USDA to do systematic reviews of the science did not meet its own standards for its review of saturated fats in 2010;
6. Although the DGAC is supposed to consult the NEL to conduct systematic reviews of the science, the 2015 DGAC did so for only 67% of the questions that required systematic reviews;
7. For a number of key reviews, the 2015 DGAC relied on work done in part by the American Heart Association and the American College of Cardiology, which are private associations supported by industry and therefore have a potential conflict of interest;
8. The DGAs, for the first time, introduce the “vegetarian diet” as one of its three, recommended “Dietary Patterns,” yet a NEL review of this diet concluded that the evidence for this its disease-fighting powers is only “limited,” which is the lowest rank of evidence assigned for available data;
9. The DGA’s three recommended “Dietary Patterns” are supported by only limited evidence. The NEL review found only “limited” or “insufficient” evidence that the diets could combat diabetes and only “moderate” evidence that the diets can help people lose weight. The report also gave a strong rating to the evidence that its recommended diets can fight heart disease, yet here, several studies are presented, but none unambiguously supports this claim. In conclusion, the quantity of recommended diets are supported by a small quantity of rigorous evidence that only marginally supports claims that these diets can promote better health than alternatives;
10. The DGA process does not require committee members to disclose conflicts of interest and also that, for the first time, the committee chair came not from a university but from industry;
11. The 2015 DGAC conducted a number of reviews in ways that were not systematic. This allowed for the potential introduction of bias (e.g., cherry picking of the evidence).
This last claim, on the systematic nature of the DGAC reviews, is the subject of the corrections published in The BMJ this week, and refer to CSPI points #1, #2, #7, and #8 (two of which are statements in the text and two of which are in the supporting tables). I am grateful to have had the opportunity to work with The BMJ on developing this notice.
The BMJ has placed a word limit on my response. For the rest of this comment, please see: http://thebigfatsurprise.com/comment-bmj-correction-notice/
CSPI has fought for decades to eliminate saturated fats from the American food supply (so much so, that throughout the late 1980s, CSPI advocated for replacing saturated fats with trans fats and succeeded in driving up consumption of trans fats to historic levels, as described in The Big Fat Surprise, pp.227-228). CSPI has also long advocated for shifting away from animal foods containing saturated fats, towards a plant-based diet based on grains and industrial vegetable oils. The researchers who joined CSPI in signing the letter are largely adherents to this view; many have participated in generating the science that has been used to support the hypothesis that fat and cholesterol cause heart disease, and it is upon this hypothesis that the Guidelines have been based.
Competing interests: I have read and understood BMJ policy on declaration of interests and declare that I am the author of The Big Fat Surprise (Simon & Schuster, 2014), on the history, science, and politics of dietary fat recommendations. I have received modest honorariums for presenting my research findings presented in the book to a variety of groups related to the medical, restaurant, financial, meat, and dairy industries. I am also a board member of a non-profit organization, the Nutrition Coalition, dedicated to ensuring that nutrition policy is based on rigorous science.