Dietary Patterns and Meal Timing to Achieve a Healthy Body Weight and Promote Cardiometabolic Health

The prevalence of obesity among adults in the United States has risen to 41.9%, whereas 19.7% of US children and adolescents are obese.1 Adiposity is associated with a higher risk for diabetes, cardiovascular disease, and all-cause mortality.2 Strategies to address the obesity epidemic include individual, family, and community approaches. Lifestyle interventions to achieve a healthy body weight through modification of eating patterns and eating behaviors have been studied for the past several decades. Recent evidence has focused on the effectiveness of adhering to particular dietary patterns. Dietary patterns are the combination, balance, and variety of foods habitually consumed.3 The Dietary Guidelines for Americans4 and the American Heart Association have published heart-healthy dietary pattern recommendations that include fruits and vegetables, plant-based protein, fish and seafood, low-fat dairy, liquid plant oils, and avoidance of added sugars and salt.3 Mediterranean-type and Dietary Approaches to Stop Hypertension dietary patterns are consistent with these guidelines.3 In addition, popular dietary patterns marketed to the public include low-carbohydrate (CHO), low-fat, moderate-macronutrient patterns and attention to meal timing.5,6 In this “Progress in Prevention” column, we review the current evidence informed strategies to achieve a healthy body weight and improve cardiometabolic health through modification of dietary patterns and/or meal timing. Calorie restriction has been associated with weight loss and improved cardiometabolic health.7 Cardiometabolic benefits include lower blood pressure,5 improved lipids,8 and improved insulin sensitivity.9 A variety of dietary patterns have been proposed to achieve these outcomes. Popular dietary patterns include low-CHO (<40% kcal from CHO), low-fat (<20% kcal from fat), and moderate-macronutrient (between low-CHO and low-fat) diets.10,11 A recent meta-analysis examined the pooled effect of 48 randomized controlled trials with 7286 adults on weight loss. The median age of the sample was 45.7 years, median body mass index was 33.7, and the median length of the intervention was 24 weeks. Eleven macronutrient diets were evaluated after 6 and 12 months' duration.10 The key finding was that each diet was nearly equally effective in promoting weight loss at 6 months compared with no dietary intervention. Low-CHO diets demonstrated a median weight loss difference of 8.73 kg; low-fat diets demonstrated a 7.99-kg difference at 6 months. Added behavioral support and exercise were associated with weight loss in each group. At 12 months, the weight loss of all diets compared with no diet was 1 to 2 kg less than at the 6-month endpoint. Both low-fat and low-CHO diets were more effective than the moderate-macronutrient diet patterns and all dietary interventions were better than no dietary intervention. The weight loss differences between each dietary pattern were small but effective in promoting clinically important weight loss as long as the diet was maintained. A second meta-analysis evaluated 121 randomized controlled trials (21 942 adults) on both weight loss and cardiovascular risk reduction among similar popular macronutrient diets at 6 and 12 months.5 The median age of the sample was 49 years, the median body mass index was 33, and the median length of intervention was 26 weeks. At 6 months, the low-CHO, low-fat, and moderate-macronutrient diets demonstrated a greater weight loss compared with the usual diet (4.63, 4.37, and 3.06 kg, respectively). All 3 dietary patterns also resulted in lower systolic and diastolic blood pressures than the usual diet (5.14, 5.05, and 3.48 mm reduction in systolic blood pressure, respectively, for the low-CHO, low-fat, and modified-macronutrient diets, and 3.21, 2.85, and 1.88 mm reduction in diastolic blood pressure, respectively, for each diet). Low-CHO diets were also associated with increased cardioprotective high-density lipoprotein (2.31 mg/dL) and lower low-density lipoprotein (LDL) (1.01 mg/dL) levels, whereas low-fat diets were associated with a greater reduction in LDL (7.08 mg/dL) compared with the usual diet. At 12 months' duration, improvements in body weight were reduced by 1 to 2 kg and improvements in cardiovascular risk factors returned to baseline for most dietary patterns. Taken together, any dietary weight loss intervention was effective at reducing weight and improving blood pressure after 6 months' duration compared with no intervention or the usual diet. Low-CHO diets were associated with improved high-density lipoprotein cholesterol, whereas low-fat and moderate-macronutrient diets demonstrated greater improvement in LDL cholesterol. Without behavioral interventions, most benefits decreased at 12 months' duration. Meal timing with intermittent fasting is a strategy in which periods of eating are alternated with periods of fasting.12 There are 2 general categories of intermittent fasting. Alternate-day fasting involves fasting for a 24-hour period followed by an unrestricted eating period. Time-restricted eating (TRE) is a pattern in which caloric intake is restricted during a specific period each day.13 One example of TRE is eating between 8 am and 4 pm every day and fasting until 8 am the next day (representing a 16-hour fast). It is hypothesized that there may be metabolic advantages to intermittent fasting. The mechanisms have not been elucidated, but hypotheses include greater fat-burning with periods of fasting, metabolic benefits from alignment with circadian biology, beneficial effects on the gut microbiome, and reduced oxidative stress.12–14 Research on alternate-day fasting has been conducted in relatively small samples and many included individuals with normal body weight. The fasting regimens included either no caloric intake for 24 hours, alternating with usual caloric intake on the subsequent day, or 25% caloric intake on fasting days, alternating with 125% on the subsequent day. Body weight was reduced in most studies; however, weight loss was not less when compared with daily energy restriction. It was also difficult for participants to adhere to the alternate day regimen because of the hunger experienced on fasting days.12,15,16 Time-restricted eating patterns restrict food intake to specific hours within the day and typically vary between skipping breakfast (eg, allowing meals between noon and 6 pm) or including breakfast but restricting meals after midafternoon. The resulting fasting period typically ranges between 12 and 20 hours.13 A meta-analysis of pooled data from 11 studies revealed a significant weight loss with TRE patterns; however, most participants consumed fewer calories as well. The studies included were both randomized trials and observational studies of healthy, normal-weight, and overweight participants. Findings from this meta-analysis do not ascertain if the weight loss observed was a result of restricted meal timing or overall reduced caloric intake.17 A more recent meta-analysis of 11 studies (all randomized trials) including only overweight or obese adults identified a significantly greater weight reduction in the TRE with caloric restriction compared with caloric restriction alone.6 Taken together, TRE may show promise in promoting weight loss but more studies are needed to separate the effect of calorie restriction from the timing of meals. Nurses functioning in clinical and community settings are frequently asked about what type of diet is best for weight loss as well as cardiometabolic health. Assessment of the individual’s normal patterns of dietary intake and as well cardiometabolic risk profile will provide essential information that will help guide and inform recommendations. In working with individual patients to develop a plan for weight loss, consideration of patient preferences and available resources, as well as findings from baseline dietary and cardiometabolic risk assessment, will likely increase adherence. Referral to a dietician may also be considered. Importantly, and as observed in numerous weight loss and risk reduction trials, without implementation of behavioral-lifestyle interventions, adherence to recommendations for modification in patterns of dietary intake will be less than optimal. Although not a point of emphasis in this column, increasing patterns of physical activity is essential for maintenance of weight loss. Equipped with knowledge and awareness of evidence-informed dietary guidelines for weight loss as well as skills and competencies with behavioral-lifestyle interventions, cardiovascular nurses are well prepared to assist patients in selecting and adhering to a pattern of dietary intake designed to reduce weight and cardiometabolic risk.