A calorie is a calorie? The myth that ruined our plates

Aim of the study: New dietary strategies have been created to treat overweight and obesity and have become popular and widely adopted. Nonetheless, they are mainly based on personal impressions and reports published in books and magazines, rather than on scientific evidence.

Results: In the short term, high-protein, low-carbohydrate diets and intermittent fasting are suggested to promote greater weight loss and could be adopted as a jumpstart. However, owing to adverse effects, caution is required. In the long term, current evidence indicates that different diets promoted similar weight loss and adherence to diets will predict their success. Finally, it is fundamental to adopt a diet that creates a negative energy balance and focuses on good food quality to promote health.

Aim of the study: Dietary macronutrient composition influences both hepatic function and aging. Previous work suggested that longevity and hepatic gene expression levels were highly responsive to dietary protein, but almost unaffected by other macronutrients.

Results: More genes in aging-related pathways (notably mTOR, IGF-1, and NF-kappaB) had significant correlations with dietary fat intake than protein and carbohydrate intake, and the pattern of gene expression changes in relation to dietary fat intake was in the opposite direction to the effect of graded levels of caloric restriction consistent with dietary fat having a negative impact on aging. We found 732, 808, and 995 serum metabolites were significantly correlated with dietary protein (5%-30%), fat (8.3%-80%), and carbohydrate (10%-80%) contents, respectively. Metabolomics pathway analysis revealed sphingosine-1-phosphate signaling was the significantly affected pathway by dietary fat content which has also been identified as significant changed metabolic pathway in the previous caloric restriction study. Our results suggest dietary fat has major impact on aging-related gene and metabolic pathways compared with other macronutrients.

Aim of the study: Much attention has been focused on fats and carbohydrates as the nutritional causes of energy overconsumption and obesity. In 2003, a model of intake regulation was proposed in which the third macronutrient, protein, is not only involved but is a primary driver of calorie intake via its interactions with carbohydrates and fats.

Results: This model, called protein leverage, posits that the strong regulation of protein intake causes the overconsumption of fats and carbohydrates (hence total energy) on diets with a low proportion of energy from protein and their underconsumption on diets with a high proportion of protein. Protein leverage has since been demonstrated in a range of animal studies and in several studies of human macronutrient regulation, and its potential role in contributing to the obesity epidemic is increasingly attracting discussion. Over recent years, however, several misconceptions about protein leverage have arisen. Our aim in this paper is to briefly outline some key aspects of the underlying theory and clarify 10 points of misunderstanding that have the potential to divert attention from the substantive issues.

Aim of the study: Dietary management is crucial for diabetes, yet the impact of macronutrient and energy intake on diabetic kidney disease (DKD) and all-cause mortality remains unclear. This study aimed to investigate these associations and to identify intake levels that were associated with the lowest odds of DKD and mortality.

Results: After multivariable adjustment, higher protein and dietary fiber intake showed significant inverse linear associations with DKD (P-trend <0.05). Compared with the lowest quartile (Q1), the highest quartile (Q4) had significantly lower DKD odds: protein (OR=0.41, 95% CI 0.21 to 0.79) and fiber (OR=0.50, 95% CI 0.31 to 0.82). The statistical inflection points associated with lower DKD odds were protein >74 g/day and fiber >14 g/day. Exploratory mediation analysis suggested that body mass index and hemoglobin partially explained the associations of proteins and fibers with DKD, respectively. Prospectively, after 48 months median follow-up (366 deaths, representing 3.36 million), only energy intake exhibited a significant U-shaped association with mortality risk (non-linear p<0.05). Mortality was lowest with daily energy intake between 1750 kcal and 1810 kcal.

Aim of the study: Nutritional status is a potentially modifiable factor associated with frailty in older adults. However, the association between macronutrient balance and frailty remains understudied and may differ by energy intake sufficiency. We examined the association between adherence to the Acceptable Macronutrient Distribution Ranges (AMDRs) and frailty by energy intake sufficiency.

Results: Among 925 energy-sufficient and 1878 energy-insufficient participants, frailty prevalence was 6.1% and 9.5%, respectively. AMDR non-adherence was associated with higher odds of frailty in energy-sufficient participants (OR, 5.58; 95% CI, 1.59-19.67) but not in energy-insufficient participants (OR, 1.08; 95% CI, 0.69-1.68). Among energy-sufficient participants, non-adherence to protein (OR, 2.63; 95% CI, 1.02-6.84) and fat (OR, 2.38; 95% CI, 1.19-4.77) AMDRs was significantly associated with frailty; carbohydrate non-adherence was borderline significant (OR, 2.15; 95% CI, 1.00-4.65). RCS analyses showed significant non-linear associations of carbohydrate and protein intake with frailty in energy-sufficient participants. AMDR non-adherence was associated with frailty primarily among older adults with sufficient energy intake. These findings suggest that energy adequacy and macronutrient distribution may represent complementary dimensions of nutritional status in relation to frailty.