Direct and indirect effects of low carbohydrate diet and high saturated fat consumption on markers of CVD risks with BMI, WC and A1C as mediators among UK adults aged 45–80 years in NDNS (2008/2009–2016/2017)
| Mediator and outcomes | Direct effect | Indirect effect | ||
| Estimate | 95% CI | Estimate | 95% CI | |
| BMI as mediator (model 1) | ||||
| HbA1c | 0.05 | −0.0 to 0.16 | 0.05 | −0.11 to 0.11** |
| TRIG | −2.47 | −4.8 to 1 72 | −3.58 | −4.56 to 4.79*** |
| Total chol | 2.36 | −1.93 to 7.03 | 3.17 | −6.55 to 6.45 |
| HDL | 1.94 | 0.5 to 3.92** | 1.06 | −2.46 to 2.29 |
| LDL | 1.31 | −3.04 to 4.41 | −3.16 | −5.87 to 5.43** |
| SBP | 1.36 | −0.03 to 3.08** | −1.66 | −2.49 to 2.42** |
| DBP | 0.67 | −0.52 to 1.31 | −0.19 | −1.59 to 1.41 |
| CRP | −0.2 | −0.63 to 0.41 | −0.41 | −0.75 to 0.75** |
| BMI and WC as mediators (model 2) | ||||
| HbA1c | 0.1 | 0.0 to 0.16** | 0.02 | −0.1 to 0.12 |
| TRIG | −0.78 | −4.09 to 2.44 | −2.28 | −4.81 to 4.77 |
| Total chol | 2.49 | −1.27 to 7.28 | −0.01 | −6.12 to 6.46 |
| HDL | 1.35 | 0.54 to 3.86 | −0.36 | −2.59 to 2.33 |
| LDL | 2.1 | −3.07 to 4.72 | −1.44 | −5.57 to 5.68 |
| SBP | 1.36 | −0.08 to 2.93** | −0.11 | −1.78 to 3.05 |
| DBP | 0.1 | −0.49 to 1.23 | 0.33 | −1.52 to 1.44 |
| CRP | 0.04 | −0.56 to 0.51 | −0.05 | −0.68 to 0.9 |
| BMI, WC, HbA1c as mediators (model 3) | ||||
| HbA1c | NA | NA | NA | NA |
| TRIG | −1.54 | −4.36 to 2 47 | −2.51 | −4.78 to 5.11 |
| Total chol | 1.86 | −0.89 to 8.18 | −0.66 | −6.28 to 5.78 |
| HDL | 2 | 0.55 to 4.24*** | 0.83 | −2.51 to 2.57 |
| LDL | −0.74 | −3.03 to 4.66 | −2.65 | −6.23 to 5.65 |
| SBP | 2.99 | 1.02 to 4.47*** | −0.11 | −1.84 to 2.91 |
| DBP | 0.79 | −0.43 to 1.67 | 0.12 | −1.34 to 1.54 |
| CRP | 0.01 | −0.44 to 0.56 | −0.21 | −0.65 to 0.85 |
The confounders for the analysis are age, sex, ethnicity, economic status, smoking status, total calories intake, alcohol intake and whether taking general medicines.
Indirect effect: the effect of diet on the outcome that is explained by the mediator.
Direct effect: the effect of diet on the outcome that is not explained by the mediator.
**p≤0.05, ***p<0.01.
BMI, body mass index; CRP, C reactive protein; CVD, cardiovascular disease; DBP, diastolic blood pressure; HbA1c, glycated haemoglobin; HDL, high-density lipoprotein; LDL, low-density lipoprotein; NA, not available; NDNS, National Diet and Nutrition Survey; SBP, systolic blood pressure; TC, total cholesterol; TRIG, triglycerides; WC, waist circumference.