Discussion
metabolic disease, weight loss, cardiovascular disease
SECONDARY, METABOLIC DISEASE, CARDIOVASCULAR DISEASE
In this secondary analysis of a randomized controlled weight loss trial for generally healthy adults with overweight and obesity, the participants most successful in reducing their BMIs were those with both higher level of adherence to their assigned diets and higher quality diets. Additionally, this HQ/HA combination was associated with clinically and statistically significant reductions in systolic and diastolic blood pressures for those assigned to follow both HLC and HLF; fasting glucose and fasting insulin concentrations improved only for those assigned to the HLC diet. For the HLC group, HA seemed to drive the associations for both systolic and diastolic blood pressures. For the HLF group, HQ seemed to drive this association for systolic blood pressure; for DBP, either HA or HQ was sufficient to see this significant difference. Also, for the HLF group, HQ was associated with improvements in triglycerides values, and HQ and adherence were associated with slight worsening of HDL cholesterol values.Within the primary analysis of the DIETFITS trial [Moreover, this analysis showed associations between high-quality diets and improvements in metabolic measures such as fasting insulin concentration and systolic and diastolic blood pressures for those following low-fat diets. Additionally, improvements in fasting glucose and insulin values were seen in the low-carbohydrate group only for those with both HQ/HA diet. Improvements in insulin values were seen in the low-carbohydrate group only for both HQ/HA and HQ/LA. Due to the exploratory nature of this analysis, it is possible that these findings were due to chance. However, given the increased risk for metabolic disease among those with overweight and obesity, adding a focus on dietary quality in weight loss dietary interventions in order to potentially reduce risk of, or improve, related conditions independent of weight loss alone is intriguing and supported by the literature [Patterns of associations between dietary adherence/quality and changes in lipids among those assigned to HLC and HLF diets were less clear. Compared with the LA/LQ subgroup, none of the other adherence/quality groups had significant changes in their LDL cholesterol values. Triglyceride concentrations improved among only the HQ/LA subgroup assigned to the low-fat diet only. HDL cholesterol concentrations worsened very slightly among the HQ/HA subgroup assigned to the low-fat diet. These findings could have been due to a number of reasons, including chance, nondietary factors, or little room to change, given baseline mean lipid values were at or very near goal levels according to current guidelines [The DIETFITS trial and this secondary analysis have several strengths. The DIETFITS trial had a large sample size (Due to the inherent limitations of a secondary analysis, participants in this study were not randomly assigned to dietary quality/dietary adherence groups, making this essentially an observational study. Another limitation is a likely bias toward the null for all outcomes. This is because the method used to divide participants into diet quality/adherence groups was splitting at the median for 12-mo change in macronutrient (i.e., fat or carbohydrate) intake and median diet quality score (i.e., HEI). Many participants clustered around the median (Further research is needed to assess the impact of dietary quality in dietary interventions aimed at weight loss and improvement in cardiovascular disease risk factors. The results of this secondary analysis suggest that rather than focusing solely on changes in macronutrient intake, such as low-carbohydrate and low-fat diets, additional benefits may be gained through emphasizing eating a high-quality diet, regardless of other dietary specifics. However, it should be noted that the quality of the diet is also influenced by macronutrient intake. To date, no studies have shown a negative impact on health of eating a high-quality diet, and countless have shown numerous health benefits. Therefore, in a clinical setting, risk-benefit calculation in deciding whether to recommend high-quality diet regardless of other dietary features is in favor of making this recommendation.