This heavily paywalled study is a more thorough analysis of something that caught my eye and was glossed over in the original publication of DIETFITS last year, which showed that weight loss was equivalent in groups of people who either ate a healthy low carbohydrate or a healthy low-fat diet.
The conclusion for some was “the diets are all the same.”
Except maybe they’re not…
The problem I noticed with DIETFITS not addressed in the main paper – worse metabolic health in the low-fat group
I took the time to dive into the supplemental materials where this information was (it wasn’t in the main paper) and made these pretty charts which show a visible tendency to insulin resistance and poorer lipid status (cholesterol,HDL, LDL, triglycerides) in the “healthy low fat” diet group.
So maybe “healthy low fat” wasn’t as “healthy.”
I didn’t have access to the raw data, this paper is an analysis of what I couldn’t analyze…
The focus on LDL in the original paper is not consistent with current science
The 12-month changes in low-density lipoprotein cholesterol concentrations significantly favored a healthy low-fat diet. High-density lipoprotein cholesterol concentrations increased significantly more and concentrations of triglycerides decreased significantly more for the healthy low-carbohydrate diet group than for the healthy low-fat diet groupGardner CD, Trepanowski JF, Del Gobbo LC, Hauser ME, Rigdon J, Ioannidis JPA, et al. on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion. JAMA [Internet]. 2018 Feb 20;319(7):667.
This is a misleading statement in my opinion because of the “favored” status given low-fat diet. This statement also invokes our profession’s laser-light focus on LDL when we now know that the overall profile (HDL, triglycerides, and more recently particle type/size) is more important for cardiovascular health.
- It is impossible to tell a patient they are better/worse off based on how their LDL goes up or down by itself. (see: Just Read: Challenging the role of LDL vs Insulin Resistance in predicting heart disease, via Kaiser Permanente data)
- The current definition of “metabolic health” does not even include LDL. (see: Just Read: Prevalence of Optimal Metabolic Health in American Adults: National Health and Nutrition Examination Survey 2009–2016 (Are you in the 12%? here’s how I am)
The dogma-challenging data here – people who increased their % of saturated fat (SFA) on the low carb (LCHF) diet:
- didn’t increase the quantity of saturated fat they ate – their overall calories decreased as well as their protein and carbohydrate intakes. This explodes the myth that an LCHF diet means eating more saturated fat.
- didn’t significantly increase their LDL cholesterol
- increased their HDL (not significantly)
- significantly decreased their triglycerides
Without getting too complicated, the low-carbohydrate group did these things better than the low fat group, who did not drop their triglycerides.
The researchers showed that the drop in triglycerides in the low carbohydrate group (a good thing for health) was strongly related to the drop in carbohydrate intake, which makes low-carbohydrate superior in this case for metabolic health.
These are similar to the findings in the paper cited below, which tend to be repeatable – an overall improvement in lipid profile when lipids are looked as a group, not as a single number (kind of like what we should do in life itself):
Despite the pitch for plant-based eating, there’s no evidence here of superiority
The term “plant-based” was sprinkled throughout the paper, however it’s acknowledged that there’s no evidence here of superiority of plant-based over plant-free:
This study did not separate the analysis between plant-and animal-based saturated fat. Thus, the differential effects of plant- and animal-based sources of saturated fat on cardiovascular outcomes should be investigated further.Shih CW, Hauser ME, Aronica L, Rigdon J, Gardner CD. Changes in blood lipid concentrations associated with changes in intake of dietary saturated fat in the context of a healthy low-carbohydrate weight-loss diet: a secondary analysis of the Diet Intervention Examining The Factors Interacting with Treatment. Am J Clin Nutr [Internet]. 2019 [cited 2019 Jan 21]
“investigated further” is translated into english as “we failed to prove this” 🙂
Shifting the emphasis to weight loss (not as important) to metabolic health (more important)
The conclusion of the paper is well stated:
Specifically, these secondary analyses support shifting the focus from concern about percentage SFA intake on the overall lipid profile to instead aiming to maintain a relatively stable absolute level of saturated fat intake while focusing on improving the quality of the overall diet by incorporating more whole foods and decreasing processed carbohydrates as much as possible.Shih CW, Hauser ME, Aronica L, Rigdon J, Gardner CD. Changes in blood lipid concentrations associated with changes in intake of dietary saturated fat in the context of a healthy low-carbohydrate weight-loss diet: a secondary analysis of the Diet Intervention Examining The Factors Interacting with Treatment. Am J Clin Nutr [Internet]. 2019 [cited 2019 Jan 21]
Dislcosure: I’m in the 12% of Americans in metabolic health, and I’m not cancelling my trip to #LowCarbDenver
- By the way, I am in the 12 %, this is as a good a time as any to state that I am on a healthy fat, low carbohydrate diet
- I have no other personal interests or conflicts to disclose – conflict-free is the way to be (see: My Disclaimers and Disclosures)
See everyone there. I continue to love this century 🙂
Shih CW, Hauser ME, Aronica L, Rigdon J, Gardner CD. Changes in blood lipid concentrations associated with changes in intake of dietary saturated fat in the context of a healthy low-carbohydrate weight-loss diet: a secondary analysis of the Diet Intervention Examining The Factors Interacting with Treatment. Am J Clin Nutr [Internet]. 2019 [cited 2019 Jan 21]