Video Presentations on Diet Comparison Studies

This is What Keto Diet Does to Your Body - Prof. Christopher Gardner, PhD

Keto has been promoted as a magic bullet for weight loss by its supporters and slammed as dangerous by its opponents. It's no surprise - completely removing almost all carbohydrates is not what most people consider ‘a balanced diet’.

With carbs off the table, Keto diets involve a dramatically increased fat intake. At the same time, drastically reducing carbs means starving our gut microbes of the fiber that feeds them. 

Nonetheless, doctors prescribe keto diets to treat people with severe diabetes and see dramatic improvements, and many healthy people swear by keto for weight loss. On top of this, removing carbohydrates prevents blood sugar spikes and crashes linked to inflammation and disease. 

In today’s episode, Jonathan speaks to a leading nutritional researcher to understand whether or not keto diets are a crazy fad:

Christopher Gardner is a professor at Stanford University and a member of ZOE’s scientific advisory board who’s produced a clinical trial of keto diets, published in the American Journal of Clinical Nutrition.


Keto diet showdown! Watch Dr. Westman’s reaction to a leading nutrition researcher’s opinion of keto diets. Who you listen to and what their background is matters!

Everything You Thought You Knew About Protein Is Wrong - Stanford's Prof. Christopher Gardner, PhD

Proteins, carbs, and fats …  most people understand what the last two are. Carbs are sugars, and fat is, well, fat. It's protein that’s so important to our diets, but so often misunderstood — by the general public, that is.

Since the 1950s and 1960s, scientists have been measuring how protein affects our performance, how it supports and maintains the body’s structure, and how best to incorporate it into our diets. 

From big steaks to protein shakes, tofu to seitan, protein is more available now than ever before. With so many options, surely we’re getting enough protein? 

In today’s episode, Jonathan speaks with a leading nutritional researcher to find out.

Christopher Gardner is a professor at Stanford University and a member of ZOE’s scientific advisory board. He’s pioneering the movement to redefine how we understand the quality of our protein intake.

Low vs. High Carb Diets - Dr. Christopher Gardner, PhD

In Episode 145 I sit down with Professor Christopher Gardner from Stanford University to chat about his research looking at low versus high carb diets for weight loss.

If you’re confused about carbohydrates, fat and how to manage your body weight then I am certain you will enjoy this episode. Dr Gardner is one of the most respected nutrition scientists in the world. 

What's the BEST Diet for Humans? - Dr. Christopher Gardner, PhD

What's the healthiest diet for humans? Why does this question seem so controversial and difficult to answer? Stanford researcher Dr. Christopher Gardner addresses his findings, sources of variability and conclusions of a 20+ year career studying human nutrition.

KETOSIS DOESN'T WORK? - Dr. Westman Reacts

Dr. Westman reacts to a video in which someone claims that "low fat" and "low carb" diets are essentially the same and that reducing carbohydrates doesn't have a significant impact on insulin sensitivity.

Scholarly Articles on Diet Comparison Studies

Dietary Intervention for Overweight and Obese Adults: Comparison of Low-Carbohydrate and Low-Fat Diets. A Meta-AnalysisBackground Reduced calorie, low fat diet is currently recommended diet for overweight and obese adults. Prior data suggest that low carbohydrate diets may also be a viable option for those who are overweight and obese. Purpose Compare the effects of low carbohydrate versus low fats diet on weight and atherosclerotic cardiovascular disease risk in overweight and obese patients. Data Sources Systematic literature review via PubMed (1966–2014). Study Selection Randomized controlled trials with ≥8 weeks follow up, comparing low carbohydrate (≤120gm carbohydrates/day) and low fat diet (≤30% energy from fat/day). Data Extraction Data were extracted and prepared for analysis using double data entry. Prior to identification of candidate publications, the outcomes of change in weight and metabolic factors were selected as defined by Cochrane Collaboration. Assessment of the effects of diets on predicted risk of atherosclerotic cardiovascular disease risk was added during the data collection phase. Data Synthesis 1797 patients were included from 17 trials with <1 year follow up in 12. Compared with low fat diet, low carbohydrate was associated with significantly greater reduction in weight (Δ = -2.0 kg, 95% CI: -3.1, -0.9) and significantly lower predicted risk of atherosclerotic cardiovascular disease events (p<0.03). Frequentist and Bayesian results were concordant. The probability of greater weight loss associated with low carbohydrate was >99% while the reduction in predicted risk favoring low carbohydrate was >98%. Limitations Lack of patient-level data and heterogeneity in dropout rates and outcomes reported. Conclusions This trial-level meta-analysis of randomized controlled trials comparing LoCHO diets with LoFAT diets in strictly adherent populations demonstrates that each diet was associated with significant weight loss and reduction in predicted risk of ASCVD events. However, LoCHO diet was associated with modest but significantly greater improvements in weight loss and predicted ASCVD risk in studies from 8 weeks to 24 months in duration. These results suggest that future evaluations of dietary guidelines should consider low carbohydrate diets as effective and safe intervention for weight management in the overweight and obese, although long-term effects require further investigation.
Comparing Very Low-Carbohydrate vs DASH Diets for Overweight or Obese Adults With Hypertension and Prediabetes or Type 2 Diabetes: A Randomized TrialPURPOSE Adults with a triple multimorbidity (hypertension, prediabetes or type 2 diabetes, and overweight or obesity), are at increased risk of serious health complications, but experts disagree on which dietary patterns and support strategies should be recommended. METHODS We randomized 94 adults from southeast Michigan with this triple multimorbidity using a 2 × 2 diet-by-support factorial design, comparing a very low-carbohydrate (VLC) diet vs a Dietary Approaches to Stop Hypertension (DASH) diet, as well as comparing results with and without multicomponent extra support (mindful eating, positive emotion regulation, social support, and cooking). RESULTS Using intention-to-treat analyses, compared with the DASH diet, the VLC diet led to greater improvement in estimated mean systolic blood pressure (−9.77 mm Hg vs −5.18 mm Hg; P = .046), greater improvement in glycated hemoglobin (−0.35% vs −0.14%; P = .034), and greater improvement in weight (−19.14 lb vs −10.34 lb; P = .0003). The addition of extra support did not have a statistically significant effect on outcomes. CONCLUSIONS For adults with hypertension, prediabetes or type 2 diabetes, and overweight or obesity, the VLC diet resulted in greater improvements in systolic blood pressure, glycemic control, and weight over a 4-month period compared with the DASH diet. These findings suggest that larger trials with longer follow-up are warranted to determine whether the VLC diet might be more beneficial for disease management than the DASH diet for these high-risk adults.
Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73)Objective  To examine the traditional diet-heart hypothesis through recovery and analysis of previously unpublished data from the Minnesota Coronary Experiment (MCE) and to put findings in the context of existing diet-heart randomized controlled trials through a systematic review and meta-analysis. Design  The MCE (1968-73) is a double blind randomized controlled trial designed to test whether replacement of saturated fat with vegetable oil rich in linoleic acid reduces coronary heart disease and death by lowering serum cholesterol. Recovered MCE unpublished documents and raw data were analyzed according to hypotheses prespecified by original investigators. Further, a systematic review and meta-analyses of randomized controlled trials that lowered serum cholesterol by providing vegetable oil rich in linoleic acid in place of saturated fat without confounding by concomitant interventions was conducted. Setting  One nursing home and six state mental hospitals in Minnesota, United States. Participants  Unpublished documents with completed analyses for the randomized cohort of 9423 women and men aged 20-97; longitudinal data on serum cholesterol for the 2355 participants exposed to the study diets for a year or more; 149 completed autopsy files. Interventions  Serum cholesterol lowering diet that replaced saturated fat with linoleic acid (from corn oil and corn oil polyunsaturated margarine). Control diet was high in saturated fat from animal fats, common margarines, and shortenings. Main outcome measures  Death from all causes; association between changes in serum cholesterol and death; and coronary atherosclerosis and myocardial infarcts detected at autopsy. Results  The intervention group had significant reduction in serum cholesterol compared with controls (mean change from baseline −13.8% v −1.0%; P<0.001). Kaplan Meier graphs showed no mortality benefit for the intervention group in the full randomized cohort or for any prespecified subgroup. There was a 22% higher risk of death for each 30 mg/dL (0.78 mmol/L) reduction in serum cholesterol in covariate adjusted Cox regression models (hazard ratio 1.22, 95% confidence interval 1.14 to 1.32; P<0.001). There was no evidence of benefit in the intervention group for coronary atherosclerosis or myocardial infarcts. Systematic review identified five randomized controlled trials for inclusion (n=10 808). In meta-analyses, these cholesterol lowering interventions showed no evidence of benefit on mortality from coronary heart disease (1.13, 0.83 to 1.54) or all cause mortality (1.07, 0.90 to 1.27). Conclusions  Available evidence from randomized controlled trials shows that replacement of saturated fat in the diet with linoleic acid effectively lowers serum cholesterol but does not support the hypothesis that this translates to a lower risk of death from coronary heart disease or all causes. Findings from the Minnesota Coronary Experiment add to growing evidence that incomplete publication has contributed to overestimation of the benefits of replacing saturated fat with vegetable oils rich in linoleic acid.
Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysisObjective To evaluate the effectiveness of replacing dietary saturated fat with omega 6 linoleic acid, for the secondary prevention of coronary heart disease and death. Design Evaluation of recovered data from the Sydney Diet Heart Study, a single blinded, parallel group, randomized controlled trial conducted in 1966-73; and an updated meta-analysis including these previously missing data. Setting Ambulatory, coronary care clinic in Sydney, Australia. Participants 458 men aged 30-59 years with a recent coronary event. Interventions Replacement of dietary saturated fats (from animal fats, common margarines, and shortenings) with omega 6 linoleic acid (from safflower oil and safflower oil polyunsaturated margarine). Controls received no specific dietary instruction or study foods. All non-dietary aspects were designed to be equivalent in both groups. Outcome measures All cause mortality (primary outcome), cardiovascular mortality, and mortality from coronary heart disease (secondary outcomes). We used an intention to treat, survival analysis approach to compare mortality outcomes by group. Results The intervention group (n=221) had higher rates of death than controls (n=237) (all cause 17.6% v 11.8%, hazard ratio 1.62 (95% confidence interval 1.00 to 2.64), P=0.05; cardiovascular disease 17.2% v 11.0%, 1.70 (1.03 to 2.80), P=0.04; coronary heart disease 16.3% v 10.1%, 1.74 (1.04 to 2.92), P=0.04). Inclusion of these recovered data in an updated meta-analysis of linoleic acid intervention trials showed non-significant trends toward increased risks of death from coronary heart disease (hazard ratio 1.33 (0.99 to 1.79); P=0.06) and cardiovascular disease (1.27 (0.98 to 1.65); P=0.07). Conclusions Advice to substitute polyunsaturated fats for saturated fats is a key component of worldwide dietary guidelines for coronary heart disease risk reduction. However, clinical benefits of the most abundant polyunsaturated fatty acid, omega 6 linoleic acid, have not been established. In this cohort, substituting dietary linoleic acid in place of saturated fats increased the rates of death from all causes, coronary heart disease, and cardiovascular disease. An updated meta-analysis of linoleic acid intervention trials showed no evidence of cardiovascular benefit. These findings could have important implications for worldwide dietary advice to substitute omega 6 linoleic acid, or polyunsaturated fats in general, for saturated fats. Trial registration Clinical trials [NCT01621087][1]. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01621087&atom=%2Fbmj%2F346%2Fbmj.e8707.atom
Dietary sugar consumption and health: umbrella reviewObjective To evaluate the quality of evidence, potential biases, and validity of all available studies on dietary sugar consumption and health outcomes. Design Umbrella review of existing meta-analyses. Data sources PubMed, Embase, Web of Science, Cochrane Database of Systematic Reviews, and hand searching of reference lists. Inclusion criteria Systematic reviews and meta-analyses of randomised controlled trials, cohort studies, case-control studies, or cross sectional studies that evaluated the effect of dietary sugar consumption on any health outcomes in humans free from acute or chronic diseases. Results The search identified 73 meta-analyses and 83 health outcomes from 8601 unique articles, including 74 unique outcomes in meta-analyses of observational studies and nine unique outcomes in meta-analyses of randomised controlled trials. Significant harmful associations between dietary sugar consumption and 18 endocrine/metabolic outcomes, 10 cardiovascular outcomes, seven cancer outcomes, and 10 other outcomes (neuropsychiatric, dental, hepatic, osteal, and allergic) were detected. Moderate quality evidence suggested that the highest versus lowest dietary sugar consumption was associated with increased body weight (sugar sweetened beverages) (class IV evidence) and ectopic fatty accumulation (added sugars) (class IV evidence). Low quality evidence indicated that each serving/week increment of sugar sweetened beverage consumption was associated with a 4% higher risk of gout (class III evidence) and each 250 mL/day increment of sugar sweetened beverage consumption was associated with a 17% and 4% higher risk of coronary heart disease (class II evidence) and all cause mortality (class III evidence), respectively. In addition, low quality evidence suggested that every 25 g/day increment of fructose consumption was associated with a 22% higher risk of pancreatic cancer (class III evidence). Conclusions High dietary sugar consumption is generally more harmful than beneficial for health, especially in cardiometabolic disease. Reducing the consumption of free sugars or added sugars to below 25 g/day (approximately 6 teaspoons/day) and limiting the consumption of sugar sweetened beverages to less than one serving/week (approximately 200-355 mL/week) are recommended to reduce the adverse effect of sugars on health. Systematic review registration PROSPERO CRD42022300982. The list of all meta-analyses not selected for data extraction and reanalysis is available if needed.
Effects of unbalanced diets on cerebral glucose metabolism in the adult ratWe measured regional cerebral metabolic rates for glucose and selected cerebral metabolites in rats fed one of the following diets for 6 to 7 weeks:(1) regular laboratory chow; (2) high-fat, carbohydrate-free ketogenic diet deriving 10% of its caloric value from proteins and 90% from fat; and (3) high-carbohydrate diet deriving 10% of its caloric value from proteins, 78% from carbohydrates, and 12% from fat. In preliminary experiments, we found that moderate ketosis could not be achieved by diets deriving less than about 90% of their caloric value from fat. Rats maintained on the ketogenic diet had moderately elevated blood beta-hydroxybutyrate (0.4 mM) and acetoacetate (0.2 mM), and a five- to 10-fold increase in their cerebral beta-hydroxybutyrate level. Cerebral levels of glucose, glycogen, lactate, and citrate were similar in all groups. 2-Deoxyglucose studies showed that the ketogenic diet did not significantly alter regional brain glucose utilization. However, rats maintained on the high-carbohydrate diet had a marked decrease in their brain glucose utilization and increased cerebral concentrations of glucose 6-phosphate. These findings indicate that long-term moderate ketonemia does not significantly alter brain glucose phosphorylation. However, even marginal protein dietary deficiency, when coupled with a carbohydrate-rich diet, depresses cerebral glucose utilization to a degree often seen in metabolic encephalopathies. Our results support the clinical contention that protein dietary deficiency coupled with increased carbohydrate intake can lead to CNS dysfunction. NEUROLOGY 1995;45: 2261-2265

Scholarly Articles on the Low Carbohydrate & Ketogenic Diets (LCKD/VLCKD)

Effects of ketogenic diet on health outcomes: an umbrella review of meta-analyses of randomized clinical trials - BMC MedicineBackground Systematic reviews and meta-analyses of randomized clinical trials (RCTs) have reported the benefits of ketogenic diets (KD) in various participants such as patients with epilepsy and adults with overweight or obesity. Nevertheless, there has been little synthesis of the strength and quality of this evidence in aggregate. Methods To grade the evidence from published meta-analyses of RCTs that assessed the association of KD, ketogenic low-carbohydrate high-fat diet (K-LCHF), and very low-calorie KD (VLCKD) with health outcomes, PubMed, EMBASE, Epistemonikos, and Cochrane database of systematic reviews were searched up to February 15, 2023. Meta-analyses of RCTs of KD were included. Meta-analyses were re-performed using a random-effects model. The quality of evidence per association provided in meta-analyses was rated by the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) criteria as high, moderate, low, and very low. Results We included 17 meta-analyses comprising 68 RCTs (median [interquartile range, IQR] sample size of 42 [20–104] participants and follow-up period of 13 [8–36] weeks) and 115 unique associations. There were 51 statistically significant associations (44%) of which four associations were supported by high-quality evidence (reduced triglyceride (n = 2), seizure frequency (n = 1) and increased low-density lipoprotein cholesterol (LDL-C) (n = 1)) and four associations supported by moderate-quality evidence (decrease in body weight, respiratory exchange ratio (RER), hemoglobin A1c, and increased total cholesterol). The remaining associations were supported by very low (26 associations) to low (17 associations) quality evidence. In overweight or obese adults, VLCKD was significantly associated with improvement in anthropometric and cardiometabolic outcomes without worsening muscle mass, LDL-C, and total cholesterol. K-LCHF was associated with reduced body weight and body fat percentage, but also reduced muscle mass in healthy participants. Conclusions This umbrella review found beneficial associations of KD supported by moderate to high-quality evidence on seizure and several cardiometabolic parameters. However, KD was associated with a clinically meaningful increase in LDL-C. Clinical trials with long-term follow-up are warranted to investigate whether the short-term effects of KD will translate to beneficial effects on clinical outcomes such as cardiovascular events and mortality.

Scholarly Articles on Meat-Based/Carnivore Diets

Scholarly Articles on Fats/Saturated Fat

Scholarly Articles on Ketones

Scholarly Articles on Vegetarianism/Veganism Origins

The Global Influence of the Seventh-Day Adventist Church on DietThe emphasis on health ministry within the Seventh-day Adventist (SDA) movement led to the development of sanitariums in mid-nineteenth century America. These facilities, the most notable being in Battle Creek, Michigan, initiated the development of vegetarian foods, such as breakfast cereals and analogue meats. The SDA Church still operates a handful of food production facilities around the world. The first Battle Creek Sanitarium dietitian was co-founder of the American Dietetics Association which ultimately advocated a vegetarian diet. The SDA Church established hundreds of hospitals, colleges, and secondary schools and tens of thousands of churches around the world, all promoting a vegetarian diet. As part of the ‘health message,’ diet continues to be an important aspect of the church’s evangelistic efforts. In addition to promoting a vegetarian diet and abstinence from alcohol, the SDA church has also invested resources in demonstrating the health benefits of these practices through research. Much of that research has been conducted at Loma Linda University in southern California, where there have been three prospective cohort studies conducted over 50 years. The present study, Adventist Health Study-2, enrolled 96,194 Adventists throughout North America in 2003–2004 with funding from the National Institutes of Health. Adventist Health Studies have demonstrated that a vegetarian diet is associated with longer life and better health.

Scholarly Articles on Food "Ultraprocessing"