The pursuit of weight loss and improved health has become a central focus for many, leading to the rise of a multibillion-dollar industry filled with various therapeutic interventions. These interventions often aim to alter body composition, primarily through weight loss. However, the discussion of effective outcomes needs to go beyond merely reducing body mass. It’s about fostering lasting changes in behavior that promote health, fitness, and psychological adherence to exercise.
The Focus on Body Composition
Many intervention programs focus on the ability to alter body mass, often neglecting other physiological modifications and the alleviation of pathophysiological conditions. This singular focus on body mass alteration can lead to confusion about which therapeutic intervention provides the greatest benefit.
Research-Backed Approaches to Weight Loss and Health
For the past 20 years, research has focused on investigating the potential health benefits of various dietary components or food patterns using randomized controlled trials. These interventions have involved vegetarian diets, soy, garlic, omega-3 fats/fish oil/flax oil, antioxidants, Ginkgo biloba, and popular weight loss diets. These trials have studied outcomes that include weight, blood lipids and lipoproteins, inflammatory markers, glucose, insulin, and body composition. Most of these trials have been NIH-funded.
One impactful study is the NIH-funded weight loss diet study - DIETFITS (Diet Intervention Examining The Factors Interacting with Treatment Success) that involved randomizing 609 generally healthy, overweight/obese adults for one year to either Healthy Low-Fat or Healthy Low-Carb diet (JAMA, 2018).
Stealth Nutrition: A Novel Approach
More effective and impactful dietary improvements could be realized if public health professionals considered adding non-health related approaches to their strategies toolbox. Examples would be the connections between food and 1) global warming and climate change, 2) animal rights and welfare, and 3) human labor abuses (e.g., slaughterhouses, agriculture fields, fast food restaurants).
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One example of ongoing research in this area is a summer Food and Farm Camp run in collaboration with the Santa Clara Unified School District since 2011. Every year ~125 kids between the ages of 5-14 years come for 1-week summer camp sessions led by Stanford undergraduates and an Education Director to tend, harvest, chop, cook, and eat vegetables…and play because it is summer camp! The objective is to study the factors influencing the behaviors and preferences that lead to maximizing vegetable consumption in kids.
Institutional Food: A Systemic Approach
Universities, worksites, hospitals, and schools order and serve a lot of food, every day. If the choices offered are healthier, the consumption behaviors will be healthier. A key factor to success in institutional food is to make the food options "unapologetically delicious" a term I borrow from Greg Drescher, a colleague and friend at the Culinary Institute of America (the other CIA). Chefs are trained to make great tasting food, and chefs in institutional food settings can be part of the solution to improving eating behaviors. In 2015 I helped to initiate a Stanford-CIA collaboration that now involves dozens of universities that have agreed to collectively use their dining halls as living laboratories to study ways to maximize the synergy of taste, health and environmental sustainability.
Diet and the Microbiome: A Cutting-Edge Connection
Our lab has now partnered with the world renowned lab of Drs. Justin and Erica Sonnenburg at Stanford to conduct multiple human nutrition intervention studies. The most impactful of these studies was the Fe-Fi-Fo study (Fermented and Fiber-rich Foods) study published in Cell in 2021. In that 10-week intervention, study participants consuming more fermented foods increased their microbial diversity and decreased blood levels of ~20 inflammatory markers.
The Importance of Hypocaloric Balance and Exercise
Hypocaloric balance is necessary for changing body composition, but the effectiveness for establishing imbalance does not equate with the effectiveness for body compositional changes, or any biomarkers associated with metabolic issues. Analysis shows that there is a necessity to include exercise in combination with diet to effectively elicit changes in body composition and biomarkers of metabolic issues. More importantly, the combination, resistance training (RT) was more effective than endurance training (ET) or combination of RT and ET, particularly when progressive training volume of 2-to-3 sets for 6-to-10 reps at an intensity of ≥75% 1RM, utilizing whole body and free-weight exercises, at altering body compositional measures (ES of 0.47, 0.30, and 0.40 for loss of BM, FM, and retention of FFM respectively) and reducing total cholesterol (ES = 0.85), triglycerides (ES = 0.86) and low-density lipoproteins (ES = 0.60). Additionally RT was more effective at reducing fasting insulin levels (ES = 3.5) than ET or ET and RT. Even though generally lower ES than RT, the inclusion of ET was more effective when performed at high intensity (e.g. ≥70% VO2max or HRmax for 30-minutes 3-4x’s/wk), or in an interval training style than when utilizing the relatively common prescribed method of low-to-moderate (e.g., 50-70% VO2max or HRmax for at least equal time) steady state method, ES of 0.35, 0.39, and 0.13 for BM, FM, and FFM respectively.
The Role of Exercise and Hormones
Improvements in health appear to stem from a number of endocrinological changes that occur with both expression of overfatness and following exposure to exercise that ultimately alters the health status for the individual who is overfat. The greatest impact of these changes appears to be related to alterations in sex hormone (i.e. testosterone and androgens), growth hormone, and a host of adipokines. Low utilization of healthy behaviors elicits changes indicated to increase the risk for the development of metabolic issues, which may culminate in Type 2 Diabetes Mellitus (T2DM), and are readily associated with reduced work capacity and anabolic hormone response for the individual who is overfat.
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Addressing the Question of Low Engagement in Healthy Behaviors
Given the understanding that physical activity is beneficial to not only in body mass reduction, in particular fat mass (FM) but not fat-free mass (FFM), along with improvements in many health functions, then why are so few adults engaging in such behaviors? deaths from non-communicable diseases could be prevented, even with a possible stagnation in the total proportion of the population classified as overweight or obese via current measures. And may be related to the way in which exercise (in particular RT) is discussed in relation to the alteration of body mass, resolving metabolic issues and improvements in the overall health status for the adults who are overfat. Along with the means by which we discuss changes elicited along with the process of comparison and generalization of findings to the population large. And a methodological bias in the employment of exercise that leads to an over recommendation of a single type of exercise based on personal preference.
Meta-Analysis of Weight Loss Treatments
This systematic review explores the current understanding of changes elicited to body composition in light of the understanding related to the endocrinological and health improvements seen with the various intervention programs based solely on population-based studies. That is related to treatment utilization of diet, diet and exercise or strictly exercise intervention for means of body mass reduction (i.e. weight loss), change in blood lipids and hormone levels. In an attempt to address the question if there is a difference in response between the various methods in (not absolute loss but effect size for) loss of body mass, fat mass and fat-free mass along with changes in blood lipid profiles and hormonal levels? Upon which, analysis will examine four distinct hypotheses. First, that exercise interventions will provide a greater effectiveness means for FM reduction than any diet intervention. Second, within exercise methods the use of RT will provide a stimulus that induces a greater effectiveness for change in body mass change (reduction in FM with retention of FFM) than ET, without regard to the addition of diet to the intervention. Thirdly, exercise will provide the stimulus that is more effective than any diet intervention at reverse hormone and adipokine/cytokine signals to normal “healthy” ranges.
Methods of Analysis
Relevant studies (e.g., studies only involving human volunteers that fit into category of population based evidence) were retrieved from electronic database search engines (PubMed, EBSCO Host (CINAHL, SPORTDiscus) and Scopus) using the following key words in combination with each other: obesity, exercise, resistance training, endurance training, strength training, aerobic training, diet, adipokine (adiponectin, leptin), cytokine (CRP,IL-1, IL-6, IL-10, TNF-α), anabolic hormone(testosterone, growth hormone),thyroid hormone, insulin, inflammation, weight loss, fat mass, and fat-free mass. Study population was either identified as either “overweight” or “obese” by authors or was indicated within the study as meeting at least 1 of the classification metrics for being overweight or obese. Study designs examined chronic adaptations.
Following retrieval and evaluation for inclusion, study data (reported means and standard deviation/error for measures of interest, number of subjects in each study groups, duration of study) were entered into database for subsequent analysis. From the initial abstracts screened, a total of 66 studies were included in the meta-analysis, from which 162 study groups were included for comparison of responses within the review. Each included study was then classified by parameter of measurement and method, along with categorization of the method, of therapeutic intervention, for pooling and tabulating data for analysis based not only on the outcome of measure but for demographic information. From this pooled data for treatment responses averages, standard deviations were calculated across the studies classified by therapeutic intervention and measure of interest regardless of duration of intervention or any additional unique characteristics of the individual studies. Following which, pooled ES and confidence intervals (CI.95) of ES for each measure of interest was determined to examine the overall effect relative to a case of no change.
Standardized Effect Size
In order to complete comparisons between dissimilar experimental designs, all studies were evaluated for a standardized effect size (ES). This standardized ES across all studies was undertaken in an effort to control for difference in methods of measurement and distinct (unique) qualified differences in the therapeutic interventions. And thus allow for comparison between and within the various parameters measured based on the therapeutic intervention in a pooled fashion of ES for response. Each of measure of interest and within all groups (interventions as well as indicated control) the treatment ES were calculated via (μpost − treatment − μpre − treatment)/(σpooled within). After which, each measure of interest had a pooled ES determined between the various treatment protocol groupings and the control grouping to elicit the pooled therapeutic effect, via equation (μchange treatment − μchange control)/(σpooled with control). Additional comparison of the pooled ES for changes were made on between the responses noted in the various measures of interest across, and relative to the pooled response for the control groups, indicated in the studies included in the analysis, based on the equation, (μchange across − treatment # 1 − μchange across − treatment # 2)/(σpooled between treatment). In an effort to establish a secondary directionality for difference between treatments, the within study treatment ES were then clustered for 2x2 χ2 analysis to determine if any difference in the level of response, standardized ES, by outcome based on the measure of interest for comparison between responses based on relationship.
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Findings and Implications
There are a wide variety of results that were obtained from each of the therapeutic interventions utilized, not only for the reduction of body mass (including FM and FFM) but also for changes in adipokines, hormones, and blood lipid profiles. Such findings indicate that all treatments can be effective.
Personalized Approaches to Diet
Genomics research is advancing rapidly, and links between genes and obesity continue to be discovered and better defined. A growing number of single nucleotide polymorphisms (SNPs) in multiple genes have been shown to alter an individual's response to dietary macronutrient composition. The primary objective of this study is to confirm and expand on the preliminary results and determine if weight loss success can be increased if the dietary approach (Low Carb vs. Low Fat) is appropriately matched to an individual' s genetic predisposition (Low Carb Genotype vs.