Background Despite the rising popularity of plant-based alternative meats, there is limited evidence of the health effects of these products. Objectives We aimed to compare the effect of consuming plant-based alternative meat (Plant) as opposed to animal meat (Animal) on health factors. The primary outcome was fasting serum trimethylamine-N-oxide (TMAO). Secondary outcomes included fasting insulin-like growth factor 1, lipids, glucose, insulin, blood pressure, and weight. Methods SWAP-MEAT (The Study With Appetizing Plantfood—Meat Eating Alternatives Trial) was a single-site, randomized crossover trial with no washout period. Participants received Plant and Animal products, dietary counseling, lab assessments, microbiome assessments (16S), and anthropometric measurements. Participants were instructed to consume ≥2 servings/d of Plant compared with Animal for 8 wk each, while keeping all other foods and beverages as similar as possible between the 2 phases. Results The 36 participants who provided complete data for both crossover phases included 67% women, were 69% Caucasian, had a mean ± SD age 50 ± 14 y, and BMI 28 ± 5 kg/m2. Mean ± SD servings per day were not different by intervention sequence: 2.5 ± 0.6 compared with 2.6 ± 0.7 for Plant and Animal, respectively (P = 0.76). Mean ± SEM TMAO concentrations were significantly lower overall for Plant (2.7 ± 0.3) than for Animal (4.7 ± 0.9) (P = 0.012), but a significant order effect was observed (P = 0.023). TMAO concentrations were significantly lower for Plant among the n = 18 who received Plant second (2.9 ± 0.4 compared with 6.4 ± 1.5, Plant compared with Animal, P = 0.007), but not for the n = 18 who received Plant first (2.5 ± 0.4 compared with 3.0 ± 0.6, Plant compared with Animal, P = 0.23). Exploratory analyses of the microbiome failed to reveal possible responder compared with nonresponder factors. Mean ± SEM LDL-cholesterol concentrations (109.9 ± 4.5 compared with 120.7 ± 4.5 mg/dL, P = 0.002) and weight (78.7 ± 3.0 compared with 79.6 ± 3.0 kg, P < 0.001) were lower during the Plant phase. Conclusions Among generally healthy adults, contrasting Plant with Animal intake, while keeping all other dietary components similar, the Plant products improved several cardiovascular disease risk factors, including TMAO; there were no adverse effects on risk factors from the Plant products. This trial was registered at clinicaltrials.gov as NCT03718988.

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Adherence is a critical factor to consider when interpreting study results from randomized clinical trials (RCTs) comparing one diet to another, but it is frequently not reported by researchers. The purpose of this secondary analysis of the Keto–Med randomized trial was to provide a detailed examination and comparison of the adherence to the two study diets (Well Formulated Ketogenic Diet (WFKD) and Mediterranean Plus (Med-Plus)) under the two conditions: all food being provided (delivered) and all food being obtained by individual participants (self-provided). Diet was assessed at six time points including baseline (x1), week 4 of each phase when participants were receiving food deliveries (x2), week 12 of each phase when participants were preparing and providing food on their own (x2), and 12 weeks after participants completed both diet phases and were free to choose their own diet pattern (x1). The adherence scores for WFKD and Med-Plus were developed specifically for this study. Average adherence to the two diet patterns was very similar during both on-study time points of the intervention. Throughout the study, a wide range of adherence was observed among participants—for both diet types and during both the delivery phase and self-provided phase. Insight from this assessment of adherence may aid other researchers when answering the important question of how to improve behavioral adherence during dietary trials. This study is registered at clinicaltrials.gov NCT03810378.

Background Consensus has not been reached on what constitutes an optimal diet in individuals with prediabetes and type 2 diabetes (T2DM), especially between low-carbohydrate options. Objectives To compare two low-carbohydrate diets with 3 key similarities (incorporate non-starchy vegetables and avoid added sugars and refined grains) and 3 key differences (incorporate vs avoid legumes, fruits, and whole intact grains), for their effects on glucose control and cardiometabolic risk factors in individuals with prediabetes and T2DM. Design Keto-Med was a randomized, crossover, interventional trial. Forty participants aged ≥ 18 years with prediabetes or T2DM followed a Well Formulated Ketogenic Diet (WFKD) and Mediterranean-Plus diet (Med-Plus) for 12-weeks each, in random order. Diets shared 3 key similarities noted above. Med-Plus incorporated legumes, fruits, and whole intact grains while WFKD avoided them. Primary outcome was % change in HbA1c after 12-weeks on each diet. Secondary and exploratory outcomes included % change in body weight, fasting insulin, glucose, and blood lipids, glucose (continuous glucose monitor), and nutrient intake. Results Primary analysis had n = 33 with complete data. HbA1c did not differ between diets at 12-weeks. Triglycerides decreased more for WFKD (% change(SEM)): -16%(4%) vs -5%(6%), p = 0.02) and LDL-C was higher for WFKD (+10%(4%) vs -5%(5%), p = 0.01). Weight decreased 8%(1%) vs 7%(1%) and HDL-C increased 11%(2%) vs 7%(3%) for WFKD vs Med-Plus, respectively; however, there was a significant interaction of diet by order for both. Participants had lower intakes of fiber and 3 nutrients on WFKD vs Med-Plus. Twelve-week follow-up data suggested Med-Plus diet was more sustainable. Conclusion HbA1c was not different between diet phases after 12-weeks, but improved from baseline on both diets, likely due to several shared dietary aspects. WFKD was beneficial for greater decrease in triglycerides, but also had potential untoward risks from elevated LDL-C, and lower nutrient intakes from avoiding legumes, fruits, and whole intact grains, as well as being less sustainable. Trial Registration clinicaltrials.gov NCT03810378