Impact of a 6-week non-energy-restricted ketogenic diet on physical fitness, body composition and biochemical parameters in healthy adults

Abstract

BackgroundThe ketogenic diet (KD) is a very low-carbohydrate, high-fat and adequate-protein diet that without limiting calories induces different metabolic adaptations, eg, increased levels of circulating ketone bodies and a shift to lipid metabolism. Our objective was to assess the impact of a 6-week non-energy-restricted KD in healthy adults beyond cohorts of athletes on physical performance, body composition, and blood parameters.MethodsOur single arm, before-and-after comparison study consisted of a 6-week KD with a previous preparation period including detailed instructions during classes and individual counselling by a dietitian. Compliance with the dietary regimen was monitored by measuring urinary ketones daily, and 7-day food records. All tests were performed after an overnight fast: cardiopulmonary exercise testing via cycle sprioergometry, blood samples, body composition, indirect calorimetry, handgrip strength, and questionnaires addressing complaints and physical sensations.ResultsForty-two subjects aged 37 ± 12 years with a BMI of 23.9 ± 3.1 kg/m2 completed the study. Urinary ketosis was detectable on 97% of the days, revealing very good compliance with the KD. Mean energy intake during the study did not change from the habitual diet and 71.6, 20.9, and 7.7% of total energy intake were from fat, protein, and carbohydrates, respectively. Weight loss was −2.0 ± 1.9 kg (P < 0.001) with equal losses of fat-free and fat mass. VO2peak and peak power decreased from 2.55 ± 0.68 l/min to 2.49 ± 0.69 l/min by 2.4% (P = 0.023) and from 241 ± 57 W to 231 ± 57 W by 4.1% (P < 0.001), respectively, whereas, handgrip strength rose slightly from 40.1 ± 8.8 to 41.0 ± 9.1 kg by 2.5% (P = 0.047). The blood lipids TG and HDL-C remained unchanged, whereas total cholesterol and LDL-C increased significantly by 4.7 and 10.7%, respectively. Glucose, insulin, and IGF-1 dropped significantly by 3.0, 22.2 and 20.2%, respectively.ConclusionsWe detected a mildly negative impact from this 6-week non-energy-restricted KD on physical performance (endurance capacity, peak power and faster exhaustion). Our findings lead us to assume that a KD does not impact physical fitness in a clinically relevant manner that would impair activities of daily living and aerobic training. However, a KD may be a matter of concern in competitive athletes.Trial registration DRKS00009605, registered 08 January 2016.Electronic supplementary materialThe online version of this article (doi:10.1186/s12986-017-0175-5) contains supplementary material, which is available to authorized users.

Improved detection of lactate and β‐hydroxybutyrate using MEGA‐sLASER at 3 T

“…To demonstrate MEGA‐sLASER sensitivity to changes in Lac and BHB concentrations, two further experiments were conducted: Brain measurements (OCC, duration: 25.6 min) in a healthy subject (male, 31 years) for detection of BHB levels before and during a ketogenic diet, which was conducted as part of an interventional study . The subject was the one measured in the repeatability scans described above.…”

“…The subject was the one measured in the repeatability scans described above. The study protocol included daily monitoring of urinary ketone body concentrations using self‐testing stripes (sensitive for acetoacetate). Brain measurements (OCC, duration: 12.8 min) in three healthy subjects (male, age = (30 ± 1) years) before and shortly after an intensive anaerobic exercise (bicycle ergometer with progressively increasing resistance until exhaustion) for detection of Lac changes. In vivo experiments were approved by the institutional review board and written informed consent was obtained from all subjects prior to the examinations.…”

Ketogenic diet and testosterone increase: Is the increased cholesterol intake responsible? To what extent and under what circumstances can there be benefits?

“…3 Furthermore, while it is normal to have increased intake of dietary cholesterol through the ingestion of the food rich in fat used in the KD, Wilson et al did not quantify dietary cholesterol in their study. Meanwhile, another recent study 4 quantified daily dietary cholesterol intake in a KD protocol in which there was a similar nutritional ratio to that of Wilson et al and the value obtained was ~495 mg, thus providing better insight. 1,4 Moreover, in the study by Volek et al, the cholesterol intake with a KD was 844±351 mg/d, thus there were those whose intake of cholesterol was more than 1000 mg/d.…”

“…Meanwhile, another recent study 4 quantified daily dietary cholesterol intake in a KD protocol in which there was a similar nutritional ratio to that of Wilson et al and the value obtained was ~495 mg, thus providing better insight. 1,4 Moreover, in the study by Volek et al, the cholesterol intake with a KD was 844±351 mg/d, thus there were those whose intake of cholesterol was more than 1000 mg/d. …”

“…4 It is thus clear that with regard to the traditional lipid profile (i.e., total cholesterol, HDL, LDL and triglycerides), the main problem with the KD would appear to be its effect on serum cholesterol. 4 A hypocaloric KD is associated with an improvement of lipid profile, this most probably attributable to loss of body fat and carbohydrate restriction. However, when the KD is normocaloric it does not appear to alter the lipid profile to any significant degree, since lipid levels did not exceed the reference range.…”