Recently, the World Health Organization (WHO) released a call for comment to revise its “total fat” guidelines, which aims to update the dietary goals for the prevention of noncommunicable diseases originally established in 1989.
The Nutrition Network, together with some of its members submitted a comprehensive response showing that the current evidence supporting the limits placed on saturated fat consumption, are misplaced.
A sincere thank you to Dene Barbondy and Sarah Rice for their contributions.
Summary of Evidence:
The majority of the evidence used for the WHO recommended guidelines include a reduction in weight or BMI which is not reflective of body fat percentage or metabolic health. Studies which did look at body fat percentage had results which were concluded to be only marginally significant. More important measures of metabolic health, such as total cholesterol, LDL, HDL and triglycerides only demonstrated a small reduction or little to no effect, suggesting that metabolic health did not improve with decreased intake of dietary fat.
With regards to the Cohort studies – nearly 59% of the studies reviewed (23/39) showed no statistically significant associations between fat intake and body fat, which only included weight, BMI and abdominal circumference as measurements (not body fat percentage). 12 Studies had a positive association but again, without a proper body fat percentage these other markers are unreliable. 3 Studies had a negative association. The culmination of these cohort studies suggest that there is no reliable evidence between intake of dietary fat and body fat percentage.
Evidence to Recommendations:
Evidence suggests that limits placed on saturated fat consumption are misplaced. A focus on metabolic health markers is of greater benefit for determining health outcomes. A reduction in carbohydrate consumption rather than fat consumption (which naturally occurs when we remove processed foods from our diet) may improve metabolic health and should be considered as an option.
These expert reviews (and references) cover the main points of interest
- Astrup A, Bertram HC, Bonjour J-P, et al. WHO draft guidelines on dietary saturated and trans fatty acids: time for a new approach? BMJ. 2019;366:l4137. doi:10.1136/bmj.l4137
- Astrup A, Magkos F, Bier DM, et al. Saturated Fats and Health: A Reassessment and Proposal for Food-based Recommendations: JACC State-of -the-Art Review. Journal of the American College of Cardiology. Published online June 17, 2020. doi:10.1016/j.jacc.2020.05.077
- Leading Scientists Agree: Current Limits on Saturated Fats No Longer Justified. The Nutrition Coalition. Published March 4, 2020. https://www.nutritioncoalition.us/news/saturated-fat-limit-not-justified
- Krauss RM, Kris-Etherton PM. Public health guidelines should recommend reducing saturated fat consumption as much as possible: NO. Am J Clin Nutr. Published online June 4, 2020. doi:10.1093/ajcn/nqaa111 (ABSTRACT) & Debate CONSENSUS
Evidence for limiting dietary fat intake is flawed
Harcombe Z, Baker JS, Cooper SM, et al. Evidence from randomised controlled trials did not support the introduction of dietary fat guidelines in 1977 and 1983: a systematic review and meta-analysis. Open Heart. 2015;2(1):e000196. doi:10.1136/openhrt-2014-000196
Harcombe Z, Baker JS, Davies B. Evidence from prospective cohort studies does not support current dietary fat guidelines: a systematic review and meta-analysis. Br J Sports Med. 2017;51(24):1743-1749. doi:10.1136/bjsports-2016-096550 PDF
Thornley S, Schofield G, Zinn C, Henderson G. How reliable is the statistical evidence for limiting saturated fat intake? A fresh look at the influential Hooper meta-analysis. Internal Medicine Journal. 2019;49(11):1418-1424. doi:10.1111/imj.14325 ABSTRACT
Dietary fat intake and CVD risk/obesity/T2DM
Micha R, Mozaffarian D. Saturated Fat and Cardiometabolic Risk Factors, Coronary Heart Disease, Stroke, and Diabetes: a Fresh Look at the Evidence. Lipids. 2010;45(10):893-905. doi:10.1007/s11745-010-3393-4
Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease12345. Am J Clin Nutr. 2010;91(3):535-546. doi:10.3945/ajcn.2009.2772
Zhu Y, Bo Y, Liu Y. Dietary total fat, fatty acids intake, and risk of cardiovascular disease: a dose-response meta-analysis of cohort studies. Lipids in Health and Disease. 2019;18(1):91. doi:10.1186/s12944-019-1035-2
Neuenschwander M, Barbaresko J, Pischke CR, et al. Intake of dietary fats and fatty acids and the incidence of type 2 diabetes: A systematic review and dose-response meta-analysis of prospective observational studies. PLOS Medicine. 2020;17(12):e1003347. doi:10.1371/journal.pmed.1003347 (does favour veg fat but does not find a harmful association of saturated fatty acids with T2D incidence)
Souza RJ de, Mente A, Maroleanu A, et al. Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. BMJ. 2015;351:h3978. doi:10.1136/bmj.h3978
Kang Z-Q, Yang Y, Xiao B. Dietary saturated fat intake and risk of stroke: systematic review and dose-response meta-analysis of prospective cohort studies. Nutrition, Metabolism and Cardiovascular Diseases. Published online October 1, 2019. doi:10.1016/j.numecd.2019.09.028
Chowdhury R, Warnakula S, Kunutsor S, et al. Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis. Ann Intern Med. 2014;160(6):398-406. doi:10.7326/M13-1788
Forsythe CE, Phinney SD, Feinman RD, et al. Limited Effect of Dietary Saturated Fat on Plasma Saturated Fat in the Context of a Low Carbohydrate Diet. Lipids. 2010;45(10):947-962. doi:10.1007/s11745-010-3467-3
- Gjuladin-Hellon T, Davies IG, Penson P, Amiri Baghbadorani R. Effects of carbohydrate-restricted diets on low-density lipoprotein cholesterol levels in overweight and obese adults: a systematic review and meta-analysis. Nutr Rev. 2019;77(3):161-180. doi:10.1093/nutrit/nuy049
- Ravnskov U, de Lorgeril M, Diamond DM, et al. LDL-C does not cause cardiovascular disease: a comprehensive review of the current literature. Expert Rev Clin Pharmacol. 2018;11(10):959-970. doi:10.1080/17512433.2018.1519391
- Zinöcker MK, Svendsen K, Dankel SN. The homeoviscous adaptation to dietary lipids (HADL) model explains controversies over saturated fat, cholesterol, and cardiovascular disease risk. The American Journal of Clinical Nutrition. 2021;(nqaa322). doi:10.1093/ajcn/nqaa322
- Ramsden CE, Zamora D, Majchrzak-Hong S, et al. Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73). BMJ. 2016;353:i1246. doi:10.1136/bmj.i1246
Lower carbohydrate and ketogenic diets with higher fat content can lead to T2DM remission, reduced CVD risk, and a reduction in obesity and metabolic syndrome
Fat content is higher than WHO recommendations (i.e.>30% of total energy intake) in the studies below.
- Tay J, Thompson CH, Luscombe-Marsh ND, et al. Effects of an energy-restricted low-carbohydrate, high unsaturated fat/low saturated fat diet versus a high-carbohydrate, low-fat diet in type 2 diabetes: A 2-year randomized clinical trial. Diabetes Obes Metab. 2018;20(4):858-871. doi:10.1111/dom.13164
- Goss AM, Gower B, Soleymani T, et al. Effects of weight loss during a very low carbohydrate diet on specific adipose tissue depots and insulin sensitivity in older adults with obesity: a randomized clinical trial. Nutrition & Metabolism. 2020;17(1):64. doi:10.1186/s12986-020-00481-9
- Sondike SB, Copperman N, Jacobson MS. Effects of a low-carbohydrate diet on weight loss and cardiovascular risk factor in overweight adolescents. J Pediatr. 2003;142(3):253-258. doi:10.1067/mpd.2003.4 PDF
- Chiu S, Bergeron N, Williams PT, Bray GA, Sutherland B, Krauss RM. Comparison of the DASH (Dietary Approaches to Stop Hypertension) diet and a higher-fat DASH diet on blood pressure and lipids and lipoproteins: a randomized controlled trial1–3. The American Journal of Clinical Nutrition. 2016;103(2):341-347. doi:10.3945/ajcn.115.123281
- Kong Z, Sun S, Shi Q, Zhang H, Tong TK, Nie J. Short-Term Ketogenic Diet Improves Abdominal Obesity in Overweight/Obese Chinese Young Females. Front Physiol. 2020;11. doi:10.3389/fphys.2020.00856
- Forsythe CE, Phinney SD, Fernandez ML, et al. Comparison of low fat and low carbohydrate diets on circulating fatty acid composition and markers of inflammation. Lipids. 2008;43(1):65-77. doi:10.1007/s11745-007-3132-7 ABSTRACT
Recommendations and Supporting Information:
Evidence to reduce dietary fat is not as strong as the evidence in support of reducing dietary sugars and refined oils. Evidence to support reduction of saturated fat is weak in addition to outdated evidence being used as a measure of metabolic health (i.e. total cholesterol, LDL). Updated guidelines to support metabolic health need to be reviewed and included in making these recommendations. There should not be a cap at 30% of total dietary fat and there should not be a cap at 10% of saturated fat until all updated evidence is reviewed to include metabolic health.
Recommendations should not be taken from previous WHO guidelines on use of PUFA versus SFA. This is biased. Rather, updated evidence, from within the last 5 years, should be used in drawing conclusions as to recommended amounts. Recommendations should also not be based on other national dietary guidelines without sufficient review of their own sources of information and removal of bias.
The past dietary guidelines have been proven ineffective. Initial dietary guidelines in 1970 proposed that reducing dietary fat while increasing carbohydrate intake would minimize the risk of cardiovascular disease (Hite et al, 2010). Since then, the adoption of these guidelines has proven ineffective in combating morbid obesity and the incidence of non-communicable diseases.
It appears that decreasing saturated fat intake does not have significant effects with regards to cardiovascular events or strokes, and people are just as likely to die from the aforementioned issues when compared with individuals who consume more saturated fat (Ramsden et al, 2013). The evidence suggests that the average individual consumption of saturated fat does not have a significantly negative impact on cardiovascular health and is not associated with increased incidence of heart disease (Chowdhury et al, 2014).
Existing guidelines that are being reinstated or followed are not effective for the population. The most relevant and current evidence should be considered. These are our recommendations and the aforementioned studies support our viewpoint.