Peer-Reviewed Scientific Articles​

Effect of Lower Versus Higher Red Meat Intake on Cardiometabolic and Cancer Outcomes: A Systematic Review of Randomized Trials


Journal: Annals of Internal Medicine

Publication Date: 10/2019

Summary: Low- to very-low-certainty evidence suggests that diets restricted in red meat may have little or no effect on major cardiometabolic outcomes and cancer mortality and incidence.

Key Takeaways

Restricting meat from the diet does not have positive effects on cardiometabolic disease or cancer mortality and incidence.

There are No Good Reasons to Restrict Meat Intake

Comparison of Low Fat and Low Carbohydrate Diets on Circulating Fatty Acid Composition and Markers of Inflammation


Journal: Lipids

Publication Date: 11/2007

Summary: Abnormal distribution of plasma fatty acids and increased inflammation are prominent features of metabolic syndrome. We tested whether these components of metabolic syndrome, like dyslipidemia and glycemia, are responsive to carbohydrate restriction. Overweight men and women with atherogenic dyslipidemia consumed ad libitum diets very low in carbohydrate (VLCKD) (1504 kcal:%CHO:fat:protein = 12:59:28) or low in fat (LFD) (1478 kcal:%CHO:fat:protein = 56:24:20) for 12 weeks. In comparison to the LFD, the VLCKD resulted in an increased proportion of serum total n-6 PUFA, mainly attributed to a marked increase in arachidonate (20:4n-6), while its biosynthetic metabolic intermediates were decreased. The n-6/n-3 and arachidonic/eicosapentaenoic acid ratio also increased sharply. Total saturated fatty acids and 16:1n-7 were consistently decreased following the VLCKD. Both diets significantly decreased the concentration of several serum inflammatory markers, but there was an overall greater anti-inflammatory effect associated with the VLCKD, as evidenced by greater decreases in TNF-α, IL-6, IL-8, MCP-1, E-selectin, I-CAM, and PAI-1. Increased 20:4n-6 and the ratios of 20:4n-6/20:5n-3 and n-6/n-3 are commonly viewed as pro-inflammatory, but unexpectedly were consistently inversely associated with responses in inflammatory proteins. In summary, a very low carbohydrate diet resulted in profound alterations in fatty acid composition and reduced inflammation compared to a low fat diet.

Key Takeaways

A very low carbohydrate ketogenic diet was compared to a low fat diet. The ketogenic diet was associated with a change in lipid composition resulting in an increase in the omega-6. to omega-3 fatty acid ratio. This change is usually thought to be pro-inflammatory, but the ketogenic diet also showed a greater decrease in inflammatory blood markers. Therefore, a low carb ketogenic diet can change fatty acid distribution and decrease inflammation.

What Can A Ketogenic Diet Do To Your Lipids And Inflammatory Status?

Dietary carbohydrate restriction induces a unique metabolic state positively affecting atherogenic dyslipidemia, fatty acid partitioning, and metabolic syndrome


Journal: Progress in Lipids Research

Publication Date: 09/2008

Summary: Abnormal fatty acid metabolism and dyslipidemia play an intimate role in the pathogenesis of metabolic syndrome and cardiovascular diseases. The availability of glucose and insulin predominate as upstream regulatory elements that operate through a collection of transcription factors to partition lipids toward anabolic pathways. The unraveling of the details of these cellular events has proceeded rapidly, but their physiologic relevance to lifestyle modification has been largely ignored. Here we highlight the role of dietary input, specifically carbohydrate intake, in the mechanism of metabolic regulation germane to metabolic syndrome. The key principle is that carbohydrate, directly or indirectly through the effect of insulin, controls the disposition of excess dietary nutrients. Dietary carbohydrate modulates lipolysis, lipoprotein assembly and processing and affects the relation between dietary intake of saturated fat intake and circulating levels. Several of these processes are the subject of intense investigation at the cellular level. We see the need to integrate these cellular mechanisms with results from low-carbohydrate diet trials that have shown reduced cardiovascular risk through improvement in hepatic, intravascular, and peripheral processing of lipoproteins, alterations in fatty acid composition, and reductions in other cardiovascular risk factors, notably inflammation. From the current state of the literature, however, low-carbohydrate diets are grounded in basic metabolic principles and the data suggest that some form of carbohydrate restriction is a candidate to be the preferred dietary strategy for cardiovascular health beyond weight regulation.

Key Takeaways

Dietary carbohydrate intake is linked to the ability of the body to process the nutrients we consume by modulating fat breakdown and the assembly of fat carrier proteins in the body. This can lead to negative changes in saturated fat circulation in the body. These cellular mechanisms driven by dietary carbohydrate intake indicate that carbohydrate restriction can be an effective dietary treatment strategy for heart disease and weight loss.

Cellular Mechanisms Underlying Heart Disease Treatable With Carbohydrate Restriction

Carbohydrate restriction as the default treatment for type 2 diabetes and metabolic syndrome


Journal: Scandinavian Cardiovascular Journal

Publication Date: 02/2008

Summary: Dietary carbohydrate restriction in the treatment of diabetes and metabolic syndrome is based on an underlying principle of control of insulin secretion and the theory that insulin resistance is a response to chronic hyperglycemia and hyperinsulinemia. As such, the theory is intuitive and has substantial experimental support. It has generally been opposed by health agencies because of concern that carbohydrate will be replaced by fat, particularly saturated fat, thereby increasing the risk of cardiovascular disease as dictated by the so-called diet-heart hypothesis. Here we summarize recent data showing that, in fact, substitution of fat for carbohydrate generally improves cardiovascular risk factors. Removing the barrier of concern about dietary fat makes carbohydrate restriction a reasonable, if not the preferred method for treating type 2 diabetes and metabolic syndrome. We emphasize the ability of low carbohydrate diets to improve glycemic control, hemoglobin A1C and to reduce medication. We review evidence that such diets are effective even in the absence of weight loss.

Key Takeaways

Substitution of carbohydrates for fat, even saturated fat, in the diet improves cardiovascular risk factors, and thus this study suggests that carbohydrate restriction may be the preferred treatment for type 2 diabetes and metabolic syndrome since cardiovascular concerns have been alleviated.

Low Carb Diets Are Not A Risk To Cardiovascular Health

Carbohydrate Restriction has a More Favorable Impact on the Metabolic Syndrome than a Low Fat Diet


Journal: Lipids

Publication Date: 12/2008

Summary: We recently proposed that the biological markers improved by carbohydrate restriction were precisely those that define the metabolic syndrome (MetS), and that the common thread was regulation of insulin as a control element. We specifically tested the idea with a 12-week study comparing two hypocaloric diets (~1,500 kcal): a carbohydrate-restricted diet (CRD) (%carbohydrate:fat:protein = 12:59:28) and a low-fat diet (LFD) (56:24:20) in 40 subjects with atherogenic dyslipidemia. Both interventions led to improvements in several metabolic markers, but subjects following the CRD had consistently reduced glucose (−12%) and insulin (−50%) concentrations, insulin sensitivity (−55%), weight loss (−10%), decreased adiposity (−14%), and more favorable triacylglycerol (TAG) (−51%), HDL-C (13%) and total cholesterol/HDL-C ratio (−14%) responses. In addition to these markers for MetS, the CRD subjects showed more favorable responses to alternative indicators of cardiovascular risk: postprandial lipemia (−47%), the Apo B/Apo A-1 ratio (−16%), and LDL particle distribution. Despite a threefold higher intake of dietary saturated fat during the CRD, saturated fatty acids in TAG and cholesteryl ester were significantly decreased, as was palmitoleic acid (16:1n-7), an endogenous marker of lipogenesis, compared to subjects consuming the LFD. Serum retinol binding protein 4 has been linked to insulin-resistant states, and only the CRD decreased this marker (−20%). The findings provide support for unifying the disparate markers of MetS and for the proposed intimate connection with dietary carbohydrate. The results support the use of dietary carbohydrate restriction as an effective approach to improve features of MetS and cardiovascular risk.

Key Takeaways

Carbohydrate restriction diets showed better outcomes than low fat diets. The carbohydrate restrictive diet had a greater improvement in blood sugar, insulin, insulin sensitivity, weight loss, body fat, triglycerides, HDL, total cholesterol, and other markers for cardiovascular health.

Carbohydrate Restriction Outperforms Low Fat Diets

Systematic review of randomized controlled trials of low‐carbohydrate vs. low‐fat/low‐calorie diets in the management of obesity and its comorbidities


Journal: Obesity Reviews

Publication Date: 12/2008

Summary: There are few studies comparing the effects of low‐carbohydrate/high‐protein diets with low‐fat/high‐carbohydrate diets for obesity and cardiovascular disease risk. This systematic review focuses on randomized controlled trials of low‐carbohydrate diets compared with low‐fat/low‐calorie diets. Studies conducted in adult populations with mean or median body mass index of ≥28 kg m−2 were included. Thirteen electronic databases were searched and randomized controlled trials from January 2000 to March 2007 were evaluated. Trials were included if they lasted at least 6 months and assessed the weight‐loss effects of low‐carbohydrate diets against low‐fat/low‐calorie diets. For each study, data were abstracted and checked by two researchers prior to electronic data entry. The computer program Review Manager 4.2.2 was used for the data analysis. Thirteen articles met the inclusion criteria. There were significant differences between the groups for weight, high‐density lipoprotein cholesterol, triacylglycerols and systolic blood pressure, favouring the low‐carbohydrate diet. There was a higher attrition rate in the low‐fat compared with the low‐carbohydrate groups suggesting a patient preference for a low‐carbohydrate/high‐protein approach as opposed to the Public Health preference of a low‐fat/high‐carbohydrate diet. Evidence from this systematic review demonstrates that low‐carbohydrate/high‐protein diets are more effective at 6 months and are as effective, if not more, as low‐fat diets in reducing weight and cardiovascular disease risk up to 1 year. More evidence and longer‐term studies are needed to assess the long‐term cardiovascular benefits from the weight loss achieved using these diets.

Key Takeaways

A review of 13 different articles comparing low carbohydrate to low fat or low calorie diets showed low carbohydrate diets to have more positive effects on weight loss, HDL cholesterol, triglycerides, and blood pressure. Additionally, the low carb diets were more effective at 6 months in reducing weight and heart disease risk.

Low Carb Diets Outperform Low Calorie and Low Fat Diets

Diets with high-fat cheese, high-fat meat, or carbohydrate on cardiovascular risk markers in overweight postmenopausal women: a randomized crossover trial.


Journal: American Journal of Clinical Nutrition

Publication Date: 09/2015

Summary: Heart associations recommend limited intake of saturated fat. However, effects of saturated fat on low-density lipoprotein (LDL)-cholesterol concentrations and cardiovascular disease risk might depend on nutrients and specific saturated fatty acids (SFAs) in food. We explored the effects of cheese and meat as sources of SFAs or isocaloric replacement with carbohydrates on blood lipids, lipoproteins, and fecal excretion of fat and bile acids. The study was a randomized, crossover, open-label intervention in 14 overweight postmenopausal women. Three full-diet periods of 2-wk duration were provided separated by 2-wk washout periods. The isocaloric diets were as follows: 1) a high-cheese (96-120-g) intervention [i.e., intervention containing cheese (CHEESE)], 2) a macronutrient-matched nondairy, high-meat control [i.e., nondairy control with a high content of high-fat processed and unprocessed meat in amounts matching the saturated fat content from cheese in the intervention containing cheese (MEAT)], and 3) a nondairy, low-fat, high-carbohydrate control (i.e., nondairy low-fat control in which the energy from cheese fat and protein was isocalorically replaced by carbohydrates and lean meat (CARB). The CHEESE diet caused a 5% higher high-density lipoprotein (HDL)-cholesterol concentration (P = 0.012), an 8% higher apo A-I concentration (P < 0.001), and a 5% lower apoB:apo A-I ratio (P = 0.008) than did the CARB diet. Also, the MEAT diet caused an 8% higher HDL-cholesterol concentration (P < 0.001) and a 4% higher apo A-I concentration (P = 0.033) than did the CARB diet. Total cholesterol, LDL cholesterol, apoB, and triacylglycerol were similar with the 3 diets. Fecal fat excretion was 1.8 and 0.9 g higher with the CHEESE diet than with CARB and MEAT diets (P < 0.001 and P = 0.004, respectively) and 0.9 g higher with the MEAT diet than with the CARB diet (P = 0.005). CHEESE and MEAT diets caused higher fecal bile acid excretion than did the CARB diet (P < 0.05 and P = 0.006, respectively). The dominant type of bile acids excreted differed between CHEESE and MEAT diets. Diets with cheese and meat as primary sources of SFAs cause higher HDL cholesterol and apo A-I and, therefore, appear to be less atherogenic than is a low-fat, high-carbohydrate diet. Also, our findings confirm that cheese increases fecal fat excretion.

Key Takeaways

High meat and high cheese diets lead to higher HDL and similar concentrations of LDL and triglycerides when compared to higher carbohydrate diet.

Meat and Cheese Raise HDL

Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males.


Journal: Journal of Translational Medicine

Publication Date: 10/2016

Summary: Intermittent fasting (IF) is an increasingly popular dietary approach used for weight loss and overall health. While there is an increasing body of evidence demonstrating beneficial effects of IF on blood lipids and other health outcomes in the overweight and obese, limited data are available about the effect of IF in athletes.

Thus, the present study sought to investigate the effects of a modified IF protocol (i.e. time-restricted feeding) during resistance training in healthy resistance-trained males. Thirty-four resistance-trained males were randomly assigned to time-restricted feeding (TRF) or normal diet group (ND).

TRF subjects consumed 100 % of their energy needs in an 8-h period of time each day, with their caloric intake divided into three meals consumed at 1 p.m., 4 p.m., and 8 p.m. The remaining 16 h per 24-h period made up the fasting period.

Subjects in the ND group consumed 100 % of their energy needs divided into three meals consumed at 8 a.m., 1 p.m., and 8 p.m. Groups were matched for kilocalories consumed and macronutrient distribution (TRF 2826 ± 412.3 kcal/day, carbohydrates 53.2 ± 1.4 %, fat 24.7 ± 3.1 %, protein 22.1 ± 2.6 %, ND 3007 ± 444.7 kcal/day, carbohydrates 54.7 ± 2.2 %, fat 23.9 ± 3.5 %, protein 21.4 ± 1.8). Subjects were tested before and after 8 weeks of the assigned diet and standardized resistance training program.

Fat mass and fat-free mass were assessed by dual-energy x-ray absorptiometry and muscle area of the thigh and arm were measured using an anthropometric system. Total and free testosterone, insulin-like growth factor 1, blood glucose, insulin, adiponectin, leptin, triiodothyronine, thyroid stimulating hormone, interleukin-6, interleukin-1β, tumor necrosis factor α, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides were measured.

Bench press and leg press maximal strength, resting energy expenditure, and respiratory ratio were also tested. After 8 weeks, the 2 Way ANOVA (Time * Diet interaction) showed a decrease in fat mass in TRF compared to ND (p = 0.0448), while fat-free mass, muscle area of the arm and thigh, and maximal strength were maintained in both groups.

Testosterone and insulin-like growth factor 1 decreased significantly in TRF, with no changes in ND (p = 0.0476; p = 0.0397). Adiponectin increased (p = 0.0000) in TRF while total leptin decreased (p = 0.0001), although not when adjusted for fat mass.

Triiodothyronine decreased in TRF, but no significant changes were detected in thyroid-stimulating hormone, total cholesterol, high-density lipoprotein, low-density lipoprotein, or triglycerides. Resting energy expenditure was unchanged, but a significant decrease in respiratory ratio was observed in the TRF group.

Our results suggest that an intermittent fasting program in which all calories are consumed in an 8-h window each day, in conjunction with resistance training, could improve some health-related biomarkers, decrease fat mass, and maintain muscle mass in resistance-trained males.

Key Takeaways

16/8 time restricted feeding in conjunction with resistance training can lead to decrease in body fat without compromising strength or lean muscle mass. Respiratory ratio was also decreased with time restricted feeding suggesting increased fat burning metabolism. Of note, testosterone was decreased in the time restricted feeding group.

Time Restricted Feeding: Burn Fat, Maintain Muscle

Cardiovascular disease risk factor responses to a type 2 diabetes care model including nutritional ketosis induced by sustained carbohydrate restriction at 1 year: an open label, non-randomized, controlled study


Journal: Cardiovascular Diabetology

Publication Date: 05/2018

Summary: Cardiovascular disease (CVD) is a leading cause of death among adults with type 2 diabetes mellitus (T2D). We recently reported that glycemic control in patients with T2D can be significantly improved through a continuous care intervention (CCI) including nutritional ketosis. The purpose of this study was to examine CVD risk factors in this cohort. We investigated CVD risk factors in patients with T2D who participated in a 1 year open label, nonrandomized, controlled study. The CCI group (n = 262) received treatment from a health coach and medical provider. A usual care (UC) group (n = 87) was independently recruited to track customary T2D progression. Circulating biomarkers of cholesterol metabolism and inflammation, blood pressure (BP), carotid intima media thickness (cIMT), multifactorial risk scores and medication use were examined. A significance level of P < 0.0019 ensured two-tailed significance at the 5% level when Bonferroni adjusted for multiple comparisons. The CCI group consisted of 262 participants (baseline mean (SD): age 54 (8) year, BMI 40.4 (8.8) kg m−2). Intention-to-treat analysis (% change) revealed the following at 1-year: total LDL-particles (LDL-P) (− 4.9%, P = 0.02), small LDL-P (− 20.8%, P = 1.2 × 10−12), LDL-P size (+ 1.1%, P = 6.0 × 10−10), ApoB (− 1.6%, P = 0.37), ApoA1 (+ 9.8%, P < 10−16), ApoB/ApoA1 ratio (− 9.5%, P = 1.9 × 10−7), triglyceride/HDL-C ratio (− 29.1%, P < 10−16), large VLDL-P (− 38.9%, P = 4.2 × 10−15), and LDL-C (+ 9.9%, P = 4.9 × 10−5). Additional effects were reductions in blood pressure, high sensitivity C-reactive protein, and white blood cell count (all P < 1 × 10−7) while cIMT was unchanged. The 10-year atherosclerotic cardiovascular disease (ASCVD) risk score decreased − 11.9% (P = 4.9 × 10−5). Antihypertensive medication use was discontinued in 11.4% of CCI participants (P = 5.3 × 10−5). The UC group of 87 participants [base- line mean (SD): age 52 (10) year, BMI 36.7 (7.2) kg m−2] showed no significant changes. After adjusting for baseline differences when comparing CCI and UC groups, significant improvements for the CCI group included small LDL-P, ApoA1, triglyceride/HDL-C ratio, HDL-C, hsCRP, and LP-IR score in addition to other biomarkers that were previously reported. The CCI group showed a greater rise in LDL-C.

Key Takeaways

Type 2 diabetes is a major risk factor for cardiovascular disease, which is also the most common cause of death in type 2 diabetics. In 262 type 2 diabetics, a ketogenic diet over 1 year showed considerable improvements in cholesterol levels, reduced blood pressure, reduced inflammation markers, and a reduced cardiovascular disease risk score. These patients were compared to 87 participants who received the usual medical care. These 87 patients saw no significant change in biomarkers.

Ketogenic Diets In Type 2 Diabetics Reduces Heart Disease Risk

The Effects of Different Degrees of Carbohydrate Restriction and Carbohydrate Replacement on Cardiometabolic Risk Markers in Humans—A Systematic Review and Meta-Analysis


Journal: Nutrients

Publication Date: 04/2020

Summary: Low-carbohydrate diets (LCDs) often differ in their diet composition, which may lead to conflicting results between randomized controlled trials. Therefore, we aimed to compare the effects of different degrees of carbohydrate (CHO) restriction on cardiometabolic risk markers in humans. The experimental LCDs of 37 human trials were classified as (1) moderate-low CHO diets (<45–40 E%, n = 13), (2) low CHO diets (<40–30 E%, n = 16), and (3) very-low CHO diets (<30–3 E%; n = 8). Summary estimates of weighted mean differences (WMDs) in selected risk markers were calculated using random-effect meta-analyses. Differences between the LCD groups were assessed with univariate meta-regression analyses. Overall, the LCDs resulted in significant weight loss, reduced diastolic blood pressure BP, and increased total cholesterol and high-density lipoprotein cholesterol (HDL-C), without significant differences between the three LCD groups. Higher low-density lipoprotein cholesterol (LDL-C) concentrations were found with the very-low CHO diets compared to the moderate-low CHO diets. Decreases in triacylglycerol (TAG) concentrations were more pronounced with the low and very-low CHO diets, compared to the moderate-low CHO diets. Substitution of CHO by mainly saturated fatty acids (SFAs) increased total cholesterol, LDL-C, and HDL-C concentrations. Except for LDL-C and TAGs, effects were not related to the degree of CHO restriction. Potential effects of nutrient exchanges should be considered when following LCDs.

Key Takeaways

When comparing moderate carbohydrate intake to low and very low carbohydrate intake, the lower the carbohydrate intake the lower a person's triglycerides, and greater the increase in LDL when carbohydrates are replaced by saturated fatty acids. HDL and Total cholesterol increased when carbohydrates were replaced with saturated fat, but outcomes did not differ between moderately low and very low carbohydrate.

Replacing Carbohydrates with Fat Can Reduce Triglycerides and Raise HDL, LDL, and Total Cholesterol

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