Perspective: Obesity-an unexplained epidemic

What should I eat today? Evidence, guidelines, dietary patterns and consumer's behavior

Over the past century, dietary recommendations emphasizing food patterns as means to deliver essential nutrients have garnered widespread acceptance. The necessity for foods supplying vital nutrients and energy throughout various life stages requires the involvement of local resources and cultural practices to prevent nutrient deficiency diseases. Since the 1980s, dietary guidelines aimed at adverting chronic diseases have relied on epidemiological research to predict which dietary patterns correlate with reduced risk of chronic disease or links to health outcomes. Dietary guidelines have been broad, typically recommending avoiding excess or deficiency of single nutrients. Efforts to fine-tune these recommendations face challenges due to a scarcity of robust scientific data supporting more specific guidance across the life cycle. Consumers have become skeptical of dietary guidelines, because media coverage of new studies is often in conflict with accepted nutrition dogma. Indications to align individual and planet's health have been issued supporting the concept of sustainable dietary patterns. Whether we really have a science-based databank to support dietary guidelines is still a matter of ongoing debate, as presented in this paper.

Trends in Diet Quality Among U.S. Adults From 1999 to 2020 by Race, Ethnicity, and Socioeconomic Disadvantage

BACKGROUND

Few data have assessed trends in diet quality among U.S. adults.

OBJECTIVE

To evaluate trends in diet quality by race, ethnicity, and socioeconomic disadvantage.

DESIGN

Repeated cross-sectional study.

SETTING

United States.

PARTICIPANTS

Noninstitutionalized adults aged 20 years or older who responded to the 1999-2020 National Health and Nutrition Examination Survey (NHANES).

MEASUREMENTS

The proportion of participants meeting the targets of the validated American Heart Association (AHA) 2020 continuous diet score (based on higher intake of fruits, vegetables, whole grains, fish and shellfish, and nuts, seeds, and legumes and lower intake of sugar-sweetened beverages, processed meat, saturated fat, and sodium) and the Healthy Eating Index (HEI)-2015, and energy-adjusted consumption of their components and other individual food groups and nutrients. Poor diet was defined as less than 40% adherence to the AHA score, intermediate as 40% to 79.9% adherence, and ideal as at least 80% adherence.

RESULTS

A total of 51 703 adults were included. From 1999 to 2020, the proportion of U.S. adults with poor diet quality decreased from 48.8% to 37.4% (difference, -11.4 percentage points [95% CI, -16.8 to -5.96 percentage points]), the proportion with intermediate quality increased from 50.6% to 61.1% (difference, 10.5 percentage points [CI, 5.20 to 16.1 percentage points]), and the proportion with ideal quality increased from 0.66% to 1.58% (difference, 0.93 percentage points [CI, 0.35 to 1.51 percentage points]) (P for trend < 0.001 for each). Persistent or worsening disparities in diet quality were observed by age, sex, race and ethnicity, education, income, food security, Supplemental Nutrition Assistance Program participation, and health insurance coverage. For example, the proportion of adults with poor diet quality decreased from 47.9% to 33.0% among those with food security (P for trend < 0.001) but did not change (51.3% to 48.2%) among those experiencing food insecurity (P for trend = 0.140) (P for interaction = 0.001). Findings were similar for HEI-2015.

LIMITATIONS

Self-reported diet; cross-sectional study design.

CONCLUSION

Diet quality among U.S. adults improved modestly between 1999 and 2020, but the proportion with poor diet quality remains high, and dietary disparities persist or are worsening.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Mediterranean-Type Diet Adherence and Body Mass Index through 20 Years of Follow-Up: Results from the ATTICA Cohort Study (2002-2022)

Evidence of the association between dietary habits and long-term body weight status is scarce. This study aimed to evaluate changes in Mediterranean-type diet (MTD) adherence in relation to body weight during 20 years of follow-up. Data from n = 1582 participants from the ATTICA cohort study (2002-2022) were used. MTD adherence was assessed via MedDietScore, and body weight status via body mass index (BMI) by 3 different measurements. We found that MTD adherence and changes in this adherence were inversely related to BMI at 20 years and the mean BMI during the 20-year follow-up. In multi-adjusted linear regression models, a 1/55 increase in baseline, 10-year, and 20-year MedDietScore was associated with a decrease of 0.05-0.13 kg/m2 in BMI at 20 years and of 0.08-0.09 kg/m2 in the mean BMI. Being consistently close to the MTD for 20 years was associated with a >90% decreased risk of maintaining overweight/obesity during the 20-year period. Strong, protective, long-lasting effects of the MTD were observed, even in those who deviated from the MTD in the follow-up (41% of the sample). Our results highlight the need to focus on the overall diet quality to minimize the risk of maintaining an excessive body weight during the life-course.

Obesogens: a unifying theory for the global rise in obesity

Despite varied treatment, mitigation, and prevention efforts, the global prevalence and severity of obesity continue to worsen. Here we propose a combined model of obesity, a unifying paradigm that links four general models: the energy balance model (EBM), based on calories as the driver of weight gain; the carbohydrate-insulin model (CIM), based on insulin as a driver of energy storage; the oxidation-reduction model (REDOX), based on reactive oxygen species (ROS) as a driver of altered metabolic signaling; and the obesogens model (OBS), which proposes that environmental chemicals interfere with hormonal signaling leading to adiposity. We propose a combined OBS/REDOX model in which environmental chemicals (in air, food, food packaging, and household products) generate false autocrine and endocrine metabolic signals, including ROS, that subvert standard regulatory energy mechanisms, increase basal and stimulated insulin secretion, disrupt energy efficiency, and influence appetite and energy expenditure leading to weight gain. This combined model incorporates the data supporting the EBM and CIM models, thus creating one integrated model that covers significant aspects of all the mechanisms potentially contributing to the obesity pandemic. Importantly, the OBS/REDOX model provides a rationale and approach for future preventative efforts based on environmental chemical exposure reduction.

Nutritional management during critical illness in those with previous obesity surgery

PURPOSE OF REVIEW

The prevalence of overweight and obesity in our society is a pressing concern that has demanded immediate attention. Traditional treatments have proven ineffective for many individuals, leading to a surge in bariatric surgery as a last resort. While the rate of early and late postoperative complications may be low, when they occur, they place these patients at higher risk of requiring intensive care treatment. Therefore, it is our aim to discuss the nutritional care of these individuals.

RECENT FINDINGS

Nutritional management of critically ill postbariatric surgical patients is related to the difficulty of providing an adequate nutritional assessment, calculating the macro and micronutrient requirements, choosing the right therapy, and defining the timely moment to initiate it. The anatomic changes related to the bariatric operation pose a high risk for a nonfunctional gastrointestinal tract both in the early postoperative and late postoperative. Therefore, the route of nutrition will greatly rely on the absorptive capacity, as well as on the nutritional status, with parenteral nutrition being an early option, especially for those with high critical care severity scores. Also, these patients are known to have an altered microbiota which may influence the absorptive capacity. Immunonutrition, prebiotics, probiotics, and symbiotics may represent potential options, but there is currently little support for 'one size fits all'.

SUMMARY

The nutritional care of critically ill patients postbariatric surgery is a complex and nuanced process requiring a multifaceted precision approach. The distinct nutritional challenges of early and late postoperative patients necessitate a thorough nutritional assessment and a highly individualized nutritional care plan.

The age-related obesity paradigm: results from two large prospective cohort studies

BACKGROUND

The obesity paradigm has been a health concern globally for many years, its meaning is controversial. In this study, we assess the characteristics and causes of obesity paradigm and detail the mediation of obesity and inflammation on survival.

METHODS

The original cohort included participants from the US National Health and Nutrition Examination Survey (NHANES) from 1999 to 2018, a prospective cohort of a nationally representative sample of adult participants; the oncology validation cohort included patients from the Investigation on Nutrition Status and Clinical Outcome of Common Cancers (INSCOC) from 2013 to 2021, a prospective cohort of Chinese patients with cancer. Survival analysis was performed using weighted (NHANES) or unweighted (INSCOC) Cox survival analyses. The normal BMI group was used as a reference for all comparisons. Systemic inflammation was defined as neutrophil-to-lymphocyte ratio (NLR) > 3. Model-based causal mediation analysis was used to identify the mediators.

RESULTS

A total of 52 270 (weighted population: 528506229) participants of the NHANES [mean follow-up times: 10.2 years; mean age (SD): 47 (19.16) years] were included in the original cohort; and a total of 17 418 patients with cancer of INSCOC [mean follow-up times: 2.9 years; mean age (SD): 57.37 (11.66) years] were included in the validation cohort. In the subgroups of all the participants, the obesity paradigm was more apparent in older participants and participants with disease [HR (95% CI): age ≥ 65 years, 0.84 (0.76, 0.93); with cancer, 0.84 (0.71, 0.99); with CVD, 0.74 (0.65, 0.85)]. As aged, the protective effect of a high BMI on survival gradually increased and a high BMI showed the effect of a protective factor on older participants [for obese II, HR (95% CI): young adults, 1.91 (1.40, 2.62); middle age, 1.56 (1.28, 1.91); old adults, 0.85 (0.76, 0.96]). The aged-related obesity paradigm in patients with cancer from the NHANES was verified in the INSCOC cohorts [for obese, HR (95%CI): 0.65 (0.52, 0.81)]. The NLR is an important mediator of the effect of BMI on survival (proportion of mediation = 15.4%).

CONCLUSIONS

The obesity paradigm has a strong correlation with age. Relative to normal weight, obese in young people was association with higher all-cause mortality, and obese in elderly people was not association with higher mortality. The protection of obesity is association with systemic inflammation.

The Effect of Fat Intake with Increased Omega-6-to-Omega-3 Polyunsaturated Fatty Acid Ratio in Animal Models of Early and Late Alzheimer's Disease-like Pathogenesis

This work aims to clarify the effect of dietary polyunsaturated fatty acid (PUFA) intake on the adult brain affected by amyloid pathology. McGill-R-Thy1-APP transgenic (Tg) rat and 5xFAD Tg mouse models that represent earlier or later disease stages were employed. The animals were exposed to a control diet (CD) or an HFD based on corn oil, from young (rats) or adult (mice) ages for 24 or 10 weeks, respectively. In rats and mice, the HFD impaired reference memory in wild-type (WT) animals but did not worsen it in Tg, did not cause obesity, and did not increase triglycerides or glucose levels. Conversely, the HFD promoted stronger microglial activation in Tg vs. WT rats but had no effect on cerebral amyloid deposition. IFN-γ, IL-1β, and IL-6 plasma levels were increased in Tg rats, regardless of diet, while CXCL1 chemokine levels were increased in HFD-fed mice, regardless of genotype. Hippocampal 3-nitrotyrosine levels tended to increase in HFD-fed Tg rats but not in mice. Overall, an HFD with an elevated omega-6-to-omega-3 ratio as compared to the CD (25:1 vs. 8.4:1) did not aggravate the outcome of AD regardless of the stage of amyloid pathology, suggesting that many neurobiological processes relevant to AD are not directly dependent on PUFA intake.

Carbohydrate-insulin model: does the conventional view of obesity reverse cause and effect?

Conventional obesity treatment, based on the First Law of Thermodynamics, assumes that excess body fat gain is driven by overeating, and that all calories are metabolically alike in this regard. Hence, to lose weight one must ultimately eat less and move more. However, this prescription rarely succeeds over the long term, in part because calorie restriction elicits predictable biological responses that oppose ongoing weight loss. The carbohydrate-insulin model posits the opposite causal direction: overeating doesn't drive body fat increase; instead, the process of storing excess fat drives overeating. A diet high in rapidly digestible carbohydrates raises the insulin-to-glucagon ratio, shifting energy partitioning towards storage in adipose, leaving fewer calories for metabolically active and fuel sensing tissues. Consequently, hunger increases, and metabolic rate slows in the body's attempt to conserve energy. A small shift in substrate partitioning though this mechanism could account for the slow but progressive weight gain characteristic of common forms of obesity. From this perspective, the conventional calorie-restricted, low-fat diet amounts to symptomatic treatment, failing to target the underlying predisposition towards excess fat deposition. A dietary strategy to lower insulin secretion may increase the effectiveness of long-term weight management and chronic disease prevention. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part II)'.

A scoping review of food and nutrition literacy programs

The impact of food literacy (FL) and nutrition literacy (NL) programs on lifestyles and health is recognized in the literature, yet few studies systematize it. This study aims to deepen the understanding of FL/NL from the characterization of programs in terms of (i) theoretical foundations, conceptualization and measuring instruments; (ii) characterization of the FL/NL programs and results and (iii) limitations and future directions declared. A scoping review of original articles addressing FL/NL programs from the Web of Science, Scopus and PubMed databases published between 2015 and 2023. There was a somewhat restricted view of the construct and the absence of a clear boundary between FL and NL. Half of the studies reported theoretical foundations. The most used model was Social Cognitive Learning Theory. More significant development of programs was observed in Australia, using quasi-experimental designs. Most of the studies informed positive results. Limitations of the studies related to the sampling process, absence of a control group and lack of follow-up. It is suggested that long-term interventions consider economic, social and cultural factors. Despite that theoretical and empirical aspects should be revised, FL/NL programs are a suitable strategy to mitigate the social and health effects of inadequate nutrition.

Comprehensive assessment of chrononutrition behaviors among nationally representative adults: Insights from National Health and Nutrition Examination Survey (NHANES) data

BACKGROUND

Aligning the time of food intake, i.e., chrononutrition, with the body's circadian clock can have a significant impact on overall health, particularly cardiometabolic health. However, there is a lack of population-based information on various chrononutrition behaviors in the United States, where the prevalence of obesity is high.

OBJECTIVE

Our primary aim was to characterize chrononutrition behaviors and their 15-year trends among US adults. We also explored the temporal associations between trends in chrononutrition behaviors and trends in obesity.

DESIGN

We utilized data from 8 cycles (2003-2018) of the National Health and Nutrition Examination Survey (NHANES) on 34,470 adults (age >19 years). The clock time of food/beverage consumption was extracted from two 24-h food recalls. The following chrononutrition behaviors were defined: 1) The clock time of the first, last, and midpoint (when 50% of total daily energy was consumed) of food/beverage intake; 2) Eating window (the time elapsed between the first and last intake); 3) Late-night eating (food intake between 21:00-23:59); and 4) Eating frequency. Survey-weighted % or mean ± standard error (SE) was used to demonstrate chrononutrition behaviors and survey-weighted regression models were utilized to evaluate trends in chrononutrition behaviors, BMI, and obesity over a 15-year period.

RESULTS

Thirty five percent of US adults had long eating windows lasting 13 h or more, with 59% of individuals consuming calories after 9 PM. The patterns of food intake among American adults were skewed, with the highest proportion of their daily energy intake (36%) being consumed during dinner meals. Notable differences in chrononutrition behaviors observed among different population subgroups. Young adults and men had longer eating windows with a higher prevalence of late-night eating compared to their age- and sex-counterparts. Black individuals had shorter eating periods due to delayed breakfast, the highest proportion (68%) of late-night eating, and obtained a greater amount of energy intake from snacks compared to other racial/ethnic groups. Over the 15-year span, there were only minor changes in a few aspects of chrononutrition behaviors, including 2% reduction in the time of eating window, while most other meal timing behaviors remained unchanged. Trends in chrononutrition behaviors were disproportionately smaller than the trends in obesity rates.

CONCLUSIONS

US adults persistently consume higher amounts of daily energy intake later in the day. Despite calls for Americans to shift intake to earlier parts of the day, this study shows that there is little change in the overall population over the 15-year period reviewed.

How can physical activity facilitate a sustainable future? Reducing obesity and chronic disease

This review examines the ways in which physical activity can contribute to a sustainable future by addressing significant public health issues. The review begins by identifying obesity and ageing as two major challenges facing societies around the world due to the association of both with the risk of chronic disease. Recent developments in the understanding and treatment of obesity are examined followed by an appraisal of the role of exercise alone and in combination with other therapies in preventing and managing obesity. The review then addresses the interaction between exercise and appetite due to the central role appetite plays in the development of overweight and obesity. The final section of the review examines the potential of physical activity to combat age-related chronic disease risk including CVD, cancer and dementia. It is concluded that while bariatric surgery and pharmacotherapy are the most effective treatments for severe obesity, physical activity has a role to play facilitating and enhancing weight loss in combination with other methods. Where weight/fat reduction via exercise is less than expected this is likely due to metabolic adaptation induced by physiological changes facilitating increased energy intake and decreased energy expenditure. Physical activity has many health benefits independent of weight control including reducing the risk of developing CVD, cancer and dementia and enhancing cognitive function in older adults. Physical activity may also provide resilience for future generations by protecting against the more severe effects of global pandemics and reducing greenhouse gas emissions via active commuting.

Ultraprocessed Foods and Obesity Risk: A Critical Review of Reported Mechanisms

Epidemiologic evidence supports a positive association between ultraprocessed food (UPF) consumption and body mass index. This has led to recommendations to avoid UPFs despite very limited evidence establishing causality. Many mechanisms have been proposed, and this review critically aimed to evaluate selected possibilities for specificity, clarity, and consistency related to food choice (i.e., low cost, shelf-life, food packaging, hyperpalatability, and stimulation of hunger/suppression of fullness); food composition (i.e., macronutrients, food texture, added sugar, fat and salt, energy density, low-calorie sweeteners, and additives); and digestive processes (i.e., oral processing/eating rate, gastric emptying time, gastrointestinal transit time, and microbiome). For some purported mechanisms (e.g., fiber content, texture, gastric emptying, and intestinal transit time), data directly contrasting the effects of UPF and non-UPF intake on the indices of appetite, food intake, and adiposity are available and do not support a unique contribution of UPFs. In other instances, data are not available (e.g., microbiome and food additives) or are insufficient (e.g., packaging, food cost, shelf-life, macronutrient intake, and appetite stimulation) to judge the benefits versus the risks of UPF avoidance. There are yet other evoked mechanisms in which the preponderance of evidence indicates ingredients in UPFs actually moderate body weight (e.g., low-calorie sweetener use for weight management; beverage consumption as it dilutes energy density; and higher fat content because it reduces glycemic responses). Because avoidance of UPFs holds potential adverse effects (e.g., reduced diet quality, increased risk of food poisoning, and food wastage), it is imprudent to make recommendations regarding their role in diets before causality and plausible mechanisms have been verified.

Obesogens and Obesity: State-of-the-Science and Future Directions Summary from a Healthy Environment and Endocrine Disruptors Strategies Workshop

On September 7 and 8, 2022, Healthy Environment and Endocrine Disruptors Strategies, an Environmental Health Sciences program, convened a scientific workshop of relevant stakeholders involved in obesity, toxicology, or obesogen research to review the state of the science regarding the role of obesogenic chemicals that might be contributing to the obesity pandemic. The workshop's objectives were to examine the evidence supporting the hypothesis that obesogens contribute to the etiology of human obesity; to discuss opportunities for improved understanding, acceptance, and dissemination of obesogens as contributors to the obesity pandemic; and to consider the need for future research and potential mitigation strategies. This report details the discussions, key areas of agreement, and future opportunities to prevent obesity. The attendees agreed that environmental obesogens are real, significant, and a contributor at some degree to weight gain at the individual level and to the global obesity and metabolic disease pandemic at a societal level; moreover, it is at least, in theory, remediable.

Is the energy balance explanation of the obesity epidemic wrong?

There is a striking discrepancy in both U.S and the U.K data between obesity rates, which are increasing, and self-reported food consumption rates, which are decreasing. There are two possible explanations for this discrepancy, namely that the widely accepted energy balance interpretation of obesity is wrong or that food consumption data are somehow biased. In a comment entitled "Obesity-an unexplained epidemic", Mozzafarian (2022) challenged the Energy Balance Model (EBM) and argued for a need to replace it with a novel biological theory. This challenge is premature, because there are psychological explanations for this discrepancy, namely that individuals with overweight and obesity underreport their food consumption and that this tendency has increased in recent years. To support these hypotheses, U.S and U.K data are reviewed that used the Doubly Labeled Water method (DLW), which is the gold standard for estimating energy expenditure. Such studies find not only consistent evidence of underreporting, but also that the discrepancy between measured energy expenditure and reported calorie consumption increased over time. Two psychological explanations for this pattern are discussed.

Non-Classical Aspects of Obesity Pathogenesis and Their Relative Clinical Importance for Obesity Treatment

Obesity is a chronic disease and a major public health problem due to its association with non-communicable diseases and all-cause mortality. An increased energy intake and decreased physical activity have been long recognized as the classical parameters that contribute to the development of obesity. However, several other, non-classical factors have also been associated with obesity through various complex mechanisms. Some of them are diet related, such as diet quality, dietary habits and speed of eating. Other factors are non-dietary, such as endocrine-disrupting chemicals, sleep quality and quantity, psychotropic medications and light at night. The scope of the present narrative review is to address these non-classical factors that are implicated in the pathogenesis of obesity, to clarify their potential role in the management of obesity and, where possible, to provide some practical clinical recommendations.

Perspective: Nutrition’s Next Chapter – Bioactive Gaps & the Microbiome-Mitochondria Axis

Food has the power to heal. Our bodies transform and are transformed by the elements in food and the adage that we are what we eat is figuratively and literally true. Twentieth century nutrition science focused on decoding the processes and building blocks of this transformation -- the proteins, fats, carbohydrates, vitamins, and minerals. Twenty-first century nutrition science is aimed at better understanding the increasingly appreciated bioactives within the food matrix that help regulate this transformation - fibers, phytonutrients, bioactive fats, and ferments. Our microbiome and the mitochondria play a key function in orchestrating the role of bioactives in health and are inspiring next-generation nutritional approaches for addressing over- and undernutrition.

Obesity as a Main Threat to Future Improvements in Population Health: Policy Opportunities and Challenges

Policy Points Obesity has emerged as a main threat to future improvements in population health, and there is little evidence that the epidemic is retreating. The traditional model of "calories in, calories out," which has guided public health policy for decades, is increasingly viewed as far too simple a framing to explain the evolution of the epidemic or guide public policy. Advances in the science of obesity, coming from many fields, highlight the structural nature of the risk, which has provided an evidence base to justify and guide policies toward addressing the social and environmental drivers of obesity. Societies and researchers need to play the long game in that widespread reductions in obesity in the short run are unlikely. Nonetheless, there are opportunities. Policies specifically targeting the food environment such as taxing high-calorie beverages and foods, restricting the marketing of junk foods to children, enhancing food labeling, and improving the dietary environment at schools may yield long-run benefits.

Evidence for the carbohydrate-insulin model in a reanalysis of the Diet Intervention Examining The Factors Interacting with Treatment Success (DIETFITS) trial

BACKGROUND

The Diet Intervention Examining The Factors Interacting with Treatment Success (DIETFITS) trial demonstrated that meaningful weight loss can be achieved with either a "healthy low-carbohydrate diet" (LCD) or "healthy low-fat diet" (LFD). However, because both diets substantially decreased glycemic load (GL), the dietary factors mediating weight loss remain unclear.

OBJECTIVES

We aimed to explore the contribution of macronutrients and GL to weight loss in DIETFITS and examine a hypothesized relationship between GL and insulin secretion.

DESIGN

This study is a secondary data analysis of the DIETFITS trial, in which participants with overweight or obesity (aged 18-50 y) were randomized to a 12-mo LCD (N = 304) or LFD (N = 305).

RESULTS

Measures related to carbohydrate intake (total amount, glycemic index, added sugar, and fiber) showed strong associations with weight loss at 3-, 6-, and 12-mo time points in the full cohort, whereas those related to total fat intake showed weak to no associations. A biomarker of carbohydrate (triglyceride/HDL cholesterol ratio) predicted weight loss at all time points (3-mo: β [kg/biomarker z-score change] = 1.1, P = 3.5 × 10^-9; 6-mo: β = 1.7, P = 1.1 × 10^-9; and 12-mo: β = 2.6, P = 1.5 × 10^-15), whereas that of fat (low-density lipoprotein cholesterol + HDL cholesterol) did not (all time points: P = NS). In a mediation model, GL explained most of the observed effect of total calorie intake on weight change. Dividing the cohort into quintiles of baseline insulin secretion and GL reduction revealed evidence of effect modification for weight loss, with P = 0.0009 at 3 mo, P = 0.01 at 6 mo, and P = 0.07 at 12 mo.

CONCLUSIONS

As predicted by the carbohydrate-insulin model of obesity, weight loss in both diet groups of DIETFITS seems to have been driven by the reduction of GL more so than dietary fat or calories, an effect that may be most pronounced among those with high insulin secretion. These findings should be interpreted cautiously in view of the exploratory nature of this study.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT01826591).

Personalized Low-Protein Diet Prescription in CKD Population: Merging Evidence From Randomized Trials With Observational Data

Nutritional therapy is a cornerstone of the clinical management of chronic kidney disease (CKD). Nevertheless, randomized controlled trials often have failed to show a relevant benefit of low-protein diets in nonselected CKD populations in terms of slowing the progression of kidney disease and need for dialysis. The more the target population is selected, the less the results can be generalizable to implement in clinical practice. On the contrary, observational studies, especially if performed with patient-centered, flexible approaches, point toward an extensive implementation of dietary protein restriction in different and unselected CKD populations. The observational evidence cannot be disregarded anymore. The most recent guidelines advise implementing low-protein diets or even very-low-protein diets in all CKD patients as early as stage 3. However, the lack of data from large randomized controlled trials on unselected CKD populations as well as on specific subpopulations, such as diabetic or obese patients, which nowadays comprise the majority of CKD subjects, reduces the generalizability of the recommendations. For some patient populations, such as those encompassing very old, nephrotic, or pregnant patients, the literature is even more limited because of the lower prevalence of these conditions and diffused prejudices against reducing protein intake. This pragmatic review discusses the need for integrating information derived from randomized trials with evidence derived from observational studies to guide feasible strategies for more successful implementation of low-protein diets in the treatment of all segments of the CKD population.

Association of Plant-Based and High-Protein Diets with a Lower Obesity Risk Defined by Fat Mass in Middle-Aged and Elderly Persons with a High Genetic Risk of Obesity

Obesity has become a severe public health challenge globally. The present study aimed to identify separate and interactive dietary, genetic, and other factors that increase the risk of obesity as measured by body fat (BF) mass. We utilized a genome-wide association study to identify genetic variants associated with high fat mass (obesity; n = 10,502) and combined them to generate polygenic risk scores (PRS) of genetic variants interacting with each other in adults aged over 40 while excluding body-fat-related diseases in a city-hospital-based cohort (n = 53,828). It was validated in Ansan/Ansung plus rural cohorts (n = 13,007). We then evaluated dietary and lifestyle factors in subjects to assess what factors might help overcome a genetic propensity for higher BF. The three-SNP model included brain-derived neurotrophic factor (BDNF)_rs6265, fat-mass- and obesity-associated protein (FTO)_rs1421085, and SEC16B_rs509325. The genes with the minor alleles of ADCY3_rs6545790 and BAIAP2_rs35867081 increased their gene expression in the visceral and subcutaneous adipocytes, but their gene expression decreased in the hypothalamus in eQTL analysis. In the three-SNP model, the PRS was associated with BF mass by 1.408 and 1.396 times after adjusting covariates 1 (age, gender, survey year, residence area, education, and income) and 2 (covariates in model 1 plus energy intake, alcohol intake, regular exercise, and smoking status), respectively. However, when separating subjects by PRS of the three-SNP model, a plant-based diet was the most significant factor associated with low BF, followed by high-protein diets and lower energy intakes. They could offset the effects of high genetic risk for high BF. In conclusion, modulating nutrient intakes might overcome a high genetic risk for obesity. Dietary choices favoring more plant-based and higher-protein foods might help prevent increased BF in Asians and potentially people of other ethnicities with high polygenetic risk scores.

Associations of age, sex, and socioeconomic status with adherence to guideline recommendations on protein intake and micronutrient supplementation in patients with sleeve gastrectomy or Roux-en-Y gastric bypass

INTRODUCTION

Patients with bariatric surgery often show poor long-term compliance to recommendations for prevention of nutrient deficiency but it is unclear which factors contribute. We investigated the associations of age, sex, and socioeconomic status (SES) with adherence to guideline recommendations on protein intake and micronutrient supplementation.

METHODS

In a monocentric cross-sectional study we prospectively recruited patients with sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB) and a minimum postoperative period of 6 months. Clinical and demographic data were obtained from the patients' medical files and by questionnaire. Patients reported on supplement usage, recorded their dietary intake for seven days and underwent physical examinations including blood testing.

RESULTS

We included 35 patients (SG: n = 25, RYGB: n = 10) with a mean (+SD) postoperative period of 20.2 (±10.4) months. Distributions of age, sex and SES were comparable between the SG and RYGB groups. Non-adherence to recommended protein intake was associated with age ≥ 50 years (p = 0.041) but not sex or SES. Protein intake inversely correlated with markers of obesity. There were no significant associations of age or sex with micronutrient supplementation. Only for vitamins A (p = 0.049) and B1 (p = 0.047) higher SES was associated with greater compliance. The only manifest deficiency associated with non-adherence to micronutrient supplementation was that for folic acid (p = 0.044).

CONCLUSION

In patients after bariatric surgery, those of older age and of lower SES might have a greater risk of unfavorable outcome and may require greater attention to micronutrient and protein supplementation.

Validation of Food Compass with a healthy diet, cardiometabolic health, and mortality among U.S. adults, 1999-2018

The Food Compass is a nutrient profiling system (NPS) to characterize the healthfulness of diverse foods, beverages and meals. In a nationally representative cohort of 47,999 U.S. adults, we validated a person's individual Food Compass Score (i.FCS), ranging from 1 (least healthful) to 100 (most healthful) based on cumulative scores of items consumed, against: (a) the Healthy Eating Index (HEI) 2015; (b) clinical risk factors and health conditions; and (c) all-cause mortality. Nationally, the mean (SD) of i.FCS was 35.5 (10.9). i.FCS correlated highly with HEI-2015 (R = 0.81). After multivariable-adjustment, each one SD (10.9 point) higher i.FCS associated with more favorable BMI (-0.60 kg/m² [-0.70,-0.51]), systolic blood pressure (-0.69 mmHg [-0.91,-0.48]), diastolic blood pressure (-0.49 mmHg [-0.66,-0.32]), LDL-C (-2.01 mg/dl [-2.63,-1.40]), HDL-C (1.65 mg/d [1.44,1.85]), HbA1c (-0.02% [-0.03,-0.01]), and fasting plasma glucose (-0.44 mg/dL [-0.74,-0.15]); lower prevalence of metabolic syndrome (OR = 0.85 [0.82,0.88]), CVD (0.92 [0.88,0.96]), cancer (0.95 [0.91,0.99]), and lung disease (0.92 [0.88,0.96]); and higher prevalence of optimal cardiometabolic health (1.24 [1.16,1.32]). i.FCS also associated with lower all-cause mortality (HR = 0.93 [0.89,0.96]). Findings were similar by age, sex, race/ethnicity, education, income, and BMI. These findings support validity of Food Compass as a tool to guide public health and private sector strategies to identify and encourage healthier eating.

Competing paradigms of obesity pathogenesis: energy balance versus carbohydrate-insulin models

The obesity pandemic continues unabated despite a persistent public health campaign to decrease energy intake (“eat less”) and increase energy expenditure (“move more”). One explanation for this failure is that the current approach, based on the notion of energy balance, has not been adequately embraced by the public. Another possibility is that this approach rests on an erroneous paradigm. A new formulation of the energy balance model (EBM), like prior versions, considers overeating (energy intake > expenditure) the primary cause of obesity, incorporating an emphasis on “complex endocrine, metabolic, and nervous system signals” that control food intake below conscious level. This model attributes rising obesity prevalence to inexpensive, convenient, energy-dense, “ultra-processed” foods high in fat and sugar. An alternative view, the carbohydrate-insulin model (CIM), proposes that hormonal responses to highly processed carbohydrates shift energy partitioning toward deposition in adipose tissue, leaving fewer calories available for the body’s metabolic needs. Thus, increasing adiposity causes overeating to compensate for the sequestered calories. Here, we highlight robust contrasts in how the EBM and CIM view obesity pathophysiology and consider deficiencies in the EBM that impede paradigm testing and refinement. Rectifying these deficiencies should assume priority, as a constructive paradigm clash is needed to resolve long-standing scientific controversies and inform the design of new models to guide prevention and treatment. Nevertheless, public health action need not await resolution of this debate, as both models target processed carbohydrates as major drivers of obesity.