Low and reduced carbohydrate diets: challenges and opportunities for type 2 diabetes management and prevention

Abstract

Low-carbohydrate diets (LCD) have been promoted for weight control and type 2 diabetes (T2D) management, based on an emerging body of evidence, including meta-analyses with an indication of publication bias. Proposed definitions vary between 50 and 130 g/d, or <10 and <40 % of energy from carbohydrate, with no consensus on LCD compositional criteria. LCD are usually followed with limited consideration for other macronutrients in the overall diet composition, introducing variance in the constituent foods and in metabolic responses. For weight management, extensive evidence supports LCD as a valid weight loss treatment, up to 1–2 years. Solely lowering carbohydrate intake does not, in the medium/long term, reduce HbA1c for T2D prevention or treatment, as many mechanisms interplay. Under controlled feeding conditions, LCD are not physiologically or clinically superior to diets with higher carbohydrates for weight-loss, fat loss, energy expenditure or glycaemic outcomes; indeed, all metabolic improvements require weight loss. Long-term evidence also links the LCD pattern to increased CVD risks and mortality. LCD can lead to micronutrient deficiencies and increased LDL-cholesterol, depending on food selection to replace carbohydrates. Evidence is limited but promising regarding food choices/sources to replace high-carbohydrate foods that may alleviate the negative effects of LCD, demanding further insight into the dietary practice of medium to long term LCD followers. Long-term, high-quality studies of LCD with different food sources (animal and/or plant origins) are needed, aiming for clinical endpoints (T2D incidence and remission, cardiovascular events, mortality). Ensuring micronutrient adequacy by food selection or supplementation should be considered for people who wish to pursue long-term LCD.

Carbohydrate knowledge, dietary guideline awareness, motivations and beliefs underlying low-carbohydrate dietary behaviours

“…Assuming that 1 time per day is equivalent to 1 average portion of starchy foods, this would be equivalent to a carbohydrate content of 40 g in 1 cup of cooked pasta or rice, 27 g in 2 slices of breads or in 1 cup of bran cereals, and 54 g in 2 medium size potatoes. This level of carbohydrate intake is to some extent in line with a very low-carbohydrate diet (< 50 g/day) 1,12 . Although other carbohydrate-rich foods (e.g.…”

“…Values are n (%) unless otherwise indicated. 1 Chi-squared test with Bonferroni adjustment for column proportion comparison (categorical data)-different letters represent significant differences between groups. 2 Kruskal-Wallis Test with Bonferroni correction for multiple tests (continuous data)-different letters represent significant differences between groups.…”

“…Food intake as assessed by the dietary targets monitor (DTM). 1 Starchy food was the sum of breads, cereals, potatoes excluding chips, and pasta and rice. 2 Fish was the sum of white fish and oily fish.…”

“…Knowledge and perceived understanding of carbohydrates, and dietary guidelines agreement and awareness stratified by self-reported low-carbohydrate diet status. 1 Chi-squared test with Bonferroni adjustment for column proportion comparison. 2 Kruskal-Wallis Test with Bonferroni correction for multiple tests-different letters represent significant differences between groups.…”

“…Data are n (%) unless otherwise indicated. 1 Valid sample size, n = 328 (169 current followers, 159 past followers). 2 Valid sample size, n = 330 (169 current followers, 161 past followers).…”