Restricting carbohydrates and calories in the treatment of type 2 diabetes: a systematic review of the effectiveness of 'low-carbohydrate' interventions with differing energy levels

The impact of carbohydrate restriction-induced elevations in low-density lipoprotein cholesterol on progression of coronary atherosclerosis: the ketogenic diet trial study design

BACKGROUND

Despite innovations in pharmacotherapy to lower lipoprotein cholesterol and apolipoprotein B, risk factors for atherosclerotic cardiovascular disease (ASCVD), ASCVD persists as the leading global cause of mortality. Elevations in low-density lipoprotein cholesterol (LDL-C) are a well-known risk factor and have been a main target in the treatment of ASCVD. The latest research suggests that ketogenic diets are effective at improving most non-LDL-C/apolipoprotein B cardiometabolic risk factors. However, ketogenic diets can induce large increases in LDL-C to >190 mg/dl in some individuals. Interestingly, these individuals are often otherwise lean and healthy. The influence of increased levels of LDL-C resulting from a carbohydrate-restricted ketogenic diet on the progression of atherosclerosis in otherwise metabolically healthy individuals is poorly understood. This observational study aims to assess and describe the progression of coronary atherosclerosis in this population within 12 months.

METHODS

Hundred relatively lean individuals who adopted ketogenic diets and subsequently exhibited hypercholesterolemia with LDL-C to >190 mg/dl, in association with otherwise good metabolic health markers, were enrolled and observed over a period of 12 months. Participants underwent serial coronary computed tomography angiography scans to assess the progression of coronary atherosclerosis in a year.

RESULTS

Data analysis shall begin following the conclusion of the trial with results to follow.

CONCLUSION

Ketogenic diets have generated debate and raised concerns within the medical community, especially in the subset exhibiting immense elevations in LDL-C, who interestingly are lean and healthy. The relationship between elevated LDL-C and ASCVD progression in this population will provide better insight into the effects of diet-induced hypercholesterolemia.

Low-Carbohydrate Dietary Interventions for Metabolic Control in Individuals With Type 2 Diabetes Mellitus: An Overview of Systematic Reviews

CONTEXT

Dietary interventions providing different amounts of carbohydrates have been proposed as a means of achieving glycemic control and weight loss in type 2 diabetes mellitus (T2DM); however, the supporting evidence is heterogeneous, making this recommendation difficult to apply in nutritional clinical practice.

OBJECTIVE

The aim was to assess the quality of evidence from meta-analyses on low-carbohydrate (LC) dietary interventions for glycemic control, weight loss, and lipid profile in individuals with T2DM.

DATA SOURCES

The MEDLINE, Web of Science, and Scopus databases were searched until September 2023.

DATA EXTRACTION

A systematic review was conducted. Systematic reviews with meta-analysis of randomized clinical trials designed to assess glycated hemoglobin (HbA1c) reductions in individuals with T2DM were eligible. The AMSTAR-2 critical appraisal tool was used to evaluate the methodological aspects of all included studies. The GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach was used to assess the certainty of the evidence.

DATA ANALYSIS

The LC interventions were associated with a reduction in HbA1c (%) of -0.42 (-1.45 to -0.09; high certainty of evidence) without considering follow-up time; at up to 3 months of follow-up of -0.28 (-0.13 to -0.43); at up to 6 months of follow-up of -0.40 (-0.61 to -0.09); at 6 to 12 months of follow-up of -0.32 (-0.49 to 0.11); and at >12 months of follow-up time of -0.31 (-0.14 to -0.65) compared with control diets.

CONCLUSION

LC diets can help reduce HbA1c in individuals with T2DM in the short term (up to 3 months). However, dietary recommendations must always be individualized, as the studies reviewed herein analyzed different populations and used different definitions of what constitutes an LC diet.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO no. CRD42023404197.

Effect of structured diet with exercise education on anthropometry and lifestyle modification in patients with type 2 diabetes: A 12-month randomized clinical trial

AIMS

Lifestyle modification involving active engagement of specialised dietitian with diet and exercise education, can be effective as first-line treatment for diabetes.

METHODS

192 patients were enrolled with diabetes in a randomised controlled trial and followed up for one year. Ninety-four patients in the intervention group participated in a comprehensive structured diet and exercise education conducted by a specialised dietitian at ambulatory centre in the United Arab Emirates.

RESULTS

The mean difference in the change in body mass index between study groups at study exit and baseline was statistically significant (BMI difference = -1.86, 95 % CI -2.68 - -1.04, P < 0.01). The intervention group reported significant decrease in total carbohydrate and daily energy intake compared to baseline (173.7 g vs 221.1 g and 1828.5 kcal vs 2177.9 kcal, respectively). Moreover, the mean metabolic equivalents (METs) in the intervention group increased significantly at study exit from baseline compared to control group METs, with mean difference between all between-group differences after baseline of 0.63 (95 % 0.29 - 0.97, P < 0.01).

CONCLUSIONS

Structured diet and exercise counselling by specialised dietitian in ambulatory settings significantly reduced carbohydrate and daily energy intake, with improved anthropometric measurements and physical activity.

Increased low-density lipoprotein cholesterol on a low-carbohydrate diet in adults with normal but not high body weight: A meta-analysis

BACKGROUND

Low-density lipoprotein (LDL) cholesterol change with consumption of a low-carbohydrate diet (LCD) is highly variable. Identifying the source of this heterogeneity could guide clinical decision-making.

OBJECTIVES

To evaluate LDL cholesterol change in randomized controlled trials involving LCDs, with a focus on body mass index (BMI) in kg/m2.

METHODS

Three electronic indexes (Pubmed, EBSCO, and Scielo) were searched for studies between 1 January, 2003 and 20 December, 2022. Two independent reviewers identified randomized controlled trials involving adults consuming <130 g/d carbohydrate and reporting BMI and LDL cholesterol change or equivalent data. Two investigators extracted relevant data, which were validated by other investigators. Data were analyzed using a random-effects model and contrasted with results of pooled individual participant data.

RESULTS

Forty-one trials with 1379 participants and a mean intervention duration of 19.4 wk were included. In a meta-regression accounting for 51.4% of the observed variability on LCDs, mean baseline BMI had a strong inverse association with LDL cholesterol change [β = -2.5 mg/dL/BMI unit, 95% confidence interval (CI): -3.7, -1.4], whereas saturated fat amount was not significantly associated with LDL cholesterol change. For trials with mean baseline BMI <25, LDL cholesterol increased by 41 mg/dL (95% CI: 19.6, 63.3) on the LCD. By contrast, for trials with a mean of BMI 25-<35, LDL cholesterol did not change, and for trials with a mean BMI ≥35, LDL cholesterol decreased by 7 mg/dL (95% CI: -12.1, -1.3). Using individual participant data, the relationship between BMI and LDL cholesterol change was not observed on higher-carbohydrate diets.

CONCLUSIONS

A substantial increase in LDL cholesterol is likely for individuals with low but not high BMI with consumption of an LCD, findings that may help guide individualized nutritional management of cardiovascular disease risk. As carbohydrate restriction tends to improve other lipid and nonlipid risk factors, the clinical significance of isolated LDL cholesterol elevation in this context warrants investigation. This trial was registered at PROSPERO as CRD42022299278.

Thyroid markers and body composition predict LDL-cholesterol change in lean healthy women on a ketogenic diet: experimental support for the lipid energy model

Introduction

There is a large heterogeneity in LDL-cholesterol change among individuals adopting ketogenic diets. Interestingly, lean metabolically healthy individuals seem to be particularly susceptible, with an inverse association between body mass index and LDL-cholesterol change. The lipid energy model proposes that, in lean healthy individuals, carbohydrate restriction upregulates systemic lipid trafficking to meet energy demands. To test if anthropometric and energy metabolism markers predict LDL-cholesterol change during carbohydrate restriction.

Methods

Ten lean, healthy, premenopausal women who habitually consumed a ketogenic diet for ≥6 months were engaged in a three-phase crossover study consisting of continued nutritional ketosis, suppression of ketosis with carbohydrate reintroduction, and return to nutritional ketosis. Each phase lasted 21 days. The predictive performance of all available relevant variables was evaluated with the linear mixed-effects models.

Results

All body composition metrics, free T3 and total T4, were significantly associated with LDL-cholesterol change. In an interaction model with BMI and free T3, both markers were significant independent and interacting predictors of LDL-cholesterol change. Neither saturated fat, HOMA-IR, leptin, adiponectin, TSH, nor rT3 was associated with LDL-cholesterol changes.

Discussion

Among lean, healthy women undergoing carbohydrate restriction, body composition and energy metabolism markers are major drivers of LDL-cholesterol change, not saturated fat, consistent with the lipid energy model.

A web-based low carbohydrate diet intervention significantly improves glycaemic control in adults with type 2 diabetes: results of the T2Diet Study randomised controlled trial

BACKGROUND/OBJECTIVES

In people with type 2 diabetes mellitus (T2DM), low carbohydrate diets (LCD), defined as 10-<26% total energy intake from carbohydrate, have indicated improved glycaemic control and clinical outcomes. Web-based interventions can help overcome significant challenges of accessibility and availability of dietary education and support for T2DM. No previous study had evaluated a web-based LCD intervention using a randomised controlled trial (RCT) design. The objective of this study was to assess whether a web-based LCD programme provided in conjunction with standard care improves glycaemic control in adults with T2DM.

SUBJECTS/METHODS

A 16-week parallel RCT was conducted remotely during Covid-19 among the general community, recruiting adults with T2DM not on insulin aged 40-89 years. Participants were randomly assigned (1:1) to standard care plus the web-based T2Diet healthy LCD education programme (intervention) or standard care only (control). The primary outcome was haemoglobin A1c (HbA1c). Secondary outcomes were weight, body mass index (BMI), anti-glycaemic medication, dietary intake, and self-efficacy. Blinded data analysis was conducted by intention-to-treat.

RESULTS

Ninety-eight participants were enrolled, assigning 49 to each group, with 87 participants (n = 40 intervention; n = 47 control) included in outcome analysis. At 16 weeks, there was a statistically significant between-group difference favouring the intervention group, with reductions in HbA1c -0.65% (95% CI: -0.99 to -0.30; p < 0.0001), weight -3.26 kg (p < 0.0001), BMI -1.11 kg/m2 (p < 0.0001), and anti-glycaemic medication requirements -0.40 (p < 0.0001), with large effect sizes Cohen's d > 0.8.

CONCLUSION

This study demonstrated that as an adjunct to standard care, the web-based T2Diet programme significantly improved glycaemic control and clinical outcomes in adults with T2DM. In addition, the results highlight the potential to improve access and availability for people with T2DM to achieve glycaemic control and improved health through web-based dietary education and support.

Evaluation of the safety and tolerability of exogenous ketosis induced by orally administered free beta-hydroxybutyrate in healthy adult subjects

Beta-hydroxybutyrate (D-BHB) is a metabolite with intrinsic signalling activity that has gained attention as a potentially clinically useful supplement. There are available supplements for inducing ketosis: ketone salts, ketone esters and medium-chain triglycerides. Even when all of them raise D-BHB in the blood and all are safe and well tolerated, they significantly differ in their safety profile, their palatability and their price. A fourth and potentially interesting option is to use biologically identical D-BHB, which it is already commercially available in the USA (American Ketone) and Greater China (MedPHA). However, its safety and tolerability had not yet been documented in the scientific literature. We evaluated the safety and tolerability of orally administered free D-BHB in a gender and age-balanced sample of 24 asymptomatic and overtly healthy adults. No participant showed acid-base abnormalities or electrolyte abnormalities. Secondary symptoms were reported after only 6.2% of all drink takes and none of the reports described the symptom as 'severe'. The most frequently reported secondary effects (19/720 or 2.6%) were gastrointestinal discomfort, headache (7/720 or 1%) and loss of appetite (7/720 or 1%). No correlation between weight-adjusted dose and frequency of secondary symptoms was observed. Free D-BHB was a safe and well-tolerated intervention for inducing sustained exogenous ketosis. Being bioidentical, salt-free and lacking intermediate metabolites, this form of supplementation could have a larger safety spectrum than salt or alcohol-based exogenous ketones. More research is warranted to assess its clinical efficacy in those clinical scenarios in which achieving ketosis rapidly could be beneficial.

A Company Is Only as Healthy as Its Workers: A 6-Month Metabolic Health Management Pilot Program Improves Employee Health and Contributes to Cost Savings

Chronic diet-related metabolic diseases, including diabetes and obesity, impose enormous burdens on patient wellness, healthcare costs, and worker productivity. Given the interdependent nature of the human and economic costs of metabolic disease, companies should be incentivized to invest in the health of their workforce. We report data from an ongoing pilot program in which employees of a manufacturing company with obesity, prediabetes, or diabetes are being treated by a metabolic health clinic using a carbohydrate restriction, community-orientated telemedicine approach. 10 patients completed the first 6 months of the program, and all lost weight, with a mean weight reduction of 38.4 lbs (17.4 kg). Improvements in HbA1c, fasting glucose, HOMA-IR, triglycerides, C-reactive protein, and systolic blood pressure were also observed across the group. Furthermore, the 10-year risk of having a major cardiovascular event, as calculated by the American Heart Association risk calculator, decreased from a mean of 9.22 to 5.18%, representing a 44% relative risk reduction. As a result of improvements in their metabolic health, patients were able to discontinue medications, leading to an estimated annualized cost savings of USD 45,171.70. These preliminary data provide proof-of-principle that when companies invest in the metabolic health of their workers, both parties stand to gain.

Is glycaemic control associated with dietary patterns independent of weight change in people newly diagnosed with type 2 diabetes? Prospective analysis of the Early-ACTivity-In-Diabetes trial

BACKGROUND

It is unclear whether diet affects glycaemic control in type 2 diabetes (T2D), over and above its effects on bodyweight. We aimed to assess whether changes in dietary patterns altered glycaemic control independently of effects on bodyweight in newly diagnosed T2D.

METHODS

We used data from 4-day food diaries, HbA1c and potential confounders in participants of the Early-ACTivity-In-Diabetes trial measured at 0, 6 and 12 months. At baseline, a 'carb/fat balance' dietary pattern and an 'obesogenic' dietary pattern were derived using reduced-rank regression, based on hypothesised nutrient-mediated mechanisms linking dietary intake to glycaemia directly or via obesity. Relationships between 0 and 6 month change in dietary pattern scores and baseline-adjusted HbA1c at 6 months (n = 242; primary outcome) were assessed using multivariable linear regression. Models were repeated for periods 6-12 months and 0-12 months (n = 194 and n = 214 respectively; secondary outcomes).

RESULTS

Reductions over 0-6 months were observed in mean bodyweight (- 2.3 (95% CI: - 2.7, - 1.8) kg), body mass index (- 0.8 (- 0.9, - 0.6) kg/m2), energy intake (- 788 (- 953, - 624) kJ/day), and HbA1c (- 1.6 (- 2.6, -0.6) mmol/mol). Weight loss strongly associated with lower HbA1c at 0-6 months (β = - 0.70 [95% CI - 0.95, - 0.45] mmol/mol/kg lost). Average fat and carbohydrate intakes changed to be more in-line with UK healthy eating guidelines between 0 and 6 months. Dietary patterns shifting carbohydrate intakes higher and fat intakes lower were characterised by greater consumption of fresh fruit, low-fat milk and boiled/baked potatoes and eating less of higher-fat processed meats, butter/animal fats and red meat. Increases in standardised 'carb/fat balance' dietary pattern score associated with improvements in HbA1c at 6 months independent of weight loss (β = - 1.54 [- 2.96, - 0.13] mmol/mol/SD). No evidence of association with HbA1c was found for this dietary pattern at other time-periods. Decreases in 'obesogenic' dietary pattern score were associated with weight loss (β = - 0.77 [- 1.31, - 0.23] kg/SD) but not independently with HbA1c during any period.

CONCLUSIONS

Promoting weight loss should remain the primary nutritional strategy for improving glycaemic control in early T2D. However, improving dietary patterns to bring carbohydrate and fat intakes closer to UK guidelines may provide small, additional improvements in glycaemic control.

TRIAL REGISTRATION

ISRCTN92162869 . Retrospectively registered on 25 July 2005.

Body weight, diabetes incidence vascular events and survival 15 years after very low calorie diet in community medical clinics in the UK

Objective

To assess weight loss maintenance, diabetes status, mortality and morbidity 15 years after a very low calorie diet programme (VLCD) in patients with obesity.

Design

General practice data bases were interrogated for subjects coded for group therapy with VLCD in the 1990s. Causes of death, occurrence of vascular disease and remission or development of diabetes were ascertained from patient records and national stroke and cardiovascular disease data bases.

Results

325 subjects engaged in the programme and had sufficient data for analysis. Baseline characteristics were: age 47.8±12. 8 years; body mass index (BMI) 36.1±6.8 kg/m²; 79.1% female/20.9% male; 13.5% had type 2 diabetes. After 15±4 years weight had changed from 97.9±19 kg at baseline to 100±20.8 kg. 10 with diabetes at baseline were in remission at 3 months, but only two remained in remission at 5 years. 50 new cases of type 2 diabetes and 11 of impaired fasting glucose developed during follow-up. Only 5.9% who remained healthy at follow-up had maintained >10% body weight reduction. Neither diabetes incidence nor diabetes free survival were related to percentage body weight lost during VLCD. Only baseline BMI was related to development of new impaired fasting glucose or diabetes by 15 years (p=0.007). 37 subjects had a cardiovascular event. Age (p=0.000002) and degree of weight loss after VLCD (p=0.03) were significantly associated with subsequent vascular events.

Conclusion

Long-term maintenance of weight loss after VLCD was rare in this single centre retrospective study 15 years later. Glucose intolerance developed in 21.4%. Lasting remission of type 2 diabetes or prevention of later glucose intolerance were not achieved. Vascular events were more frequent in those who lost most weight. Risk management during weight regain should be studied in future to assess potential for reduction in adverse cardiovascular outcomes.