Metabolic Consequences of Weight Reduction

Obesity and overweight are considered significant health problems and have become a global challenge due to their high prevalence in almost all countries. The most appropriate mechanism to treat overweight conditions is the reduction of body weight. Weight loss is associated with metabolic changes, mostly favorable to improving the overall health of an individual. There is a direct link between weight loss and improvement in metabolic diseases such as hypertension, blood glucose, lipid profiles, sleep apnea, and comorbidities such as non-alcoholic fatty liver disease, polycystic ovarian syndrome, infertility, type 2 diabetes, etc. This article will discuss the metabolic mediators and effectors of weight management after weight loss. It will also highlight the role of the interprofessional team that includes doctors, nurses, laboratory staff, nutritionists, physiotherapists, exercise physiologists, and trainers towards helping individuals with weight maintenance after a healthy weight is achieved.

Introduction

Metabolism is a dedicated network of enzyme and metabolite-derived mechanisms that are the hallmark of life activities. A healthy metabolism is a basic necessity for a healthy life that depends on lifestyle, energy intake, and expenditure. A balanced lifestyle comprising healthy eating habits, exercise, sleep cycle, and behavioral features is the utmost regulator of healthy body weight and robust metabolism.

The present-day world is challenged by an increasing prevalence of overweight and obesity, amounting to epidemic proportions. This creates a public health concern and points to our lack of success in achieving healthy population indices in terms of healthy body weight maintenance. Increased weight parallels with several comorbidities such as type 2 diabetes, some types of cancers, cardiovascular disorders, liver and kidney diseases, digestive problems, sleep apnea, osteoarthritis, etc.

Recent research indicates that the inability to maintain a healthy weight perturbs the body's metabolic and immunological axis, increasing the risk for severe illnesses such as COVID-19 and other infectious diseases. It is notable that absolute weight loss with long-term maintenance directly correlates with improvements in all health risk factors. Maintaining a healthy body weight, especially after weight reduction, requires equalized input and energy output to regulate optimal metabolism. However, the general preference for high-tasting vis- -vis less nutritious food and a sedentary lifestyle has led to a global increase in weight and also reduced tendency of long-term maintenance of a healthy weight after effective weight loss.

It is believed that weight loss at a slow rate is better sustained than weight loss more rapidly. However, scientific evidence correlates that greater initial weight loss is positively related to long-term weight maintenance. This follows through the metabolic adaptation process, consequently leading to healthier metabolic functions. Nonetheless, healthy weight maintenance achieved through weight loss regimes also requires care and treatment, usually through diet regimes or restrictions and exercise.

Prior to understanding the consequences of weight loss on metabolism, it is imperative to recognize that at the metabolic level, weight loss is a continuous metabolic adaptation process progressing through many biochemical and physiological changes involving the role of hormones, enzyme functions, metabolite effectors, and bioenergetics.

Maintaining a healthy weight is challenging. It is shown that most individuals tend to have regained a significant amount of the lost weight within a year after weight loss. With this increased prevalence of recidivism, weight management is viewed as a chronic issue. Hence, long-term care is expected for weight management and maintenance after weight loss, and programs of over a year are currently recommended by the guidelines.

Function

Metabolism is a group of processes through which food is converted into energy to help maintain bodily function. The energy generated through biochemical pathways is usually in the form of Adenosine triphosphate (ATP). A continuous supply of ATP to meet the body's energy demands during activity and rest is fundamental to the metabolic processes that sustain life. During the resting stage, the body requires energy to support activities such as breathing, maintaining blood circulation, brain function, cellular growth and repair, basic hormonal and neurological changes, etc. The calories needed for maintaining basal (resting phase) metabolism is called basal metabolic rate (BMR).

BMR increases with a decrease in body weight to about .02 kcal/min, corresponding to each % decrease in body weight. Healthy body weight is calculated by the measurement of body mass index (BMI). It assesses the body weight of an individual relative to their height and hence provides a more distinctive account of body fat content than just the weight. Though BMI does not directly measure body fat, it is a useful and inexpensive screening method for clinical and research purposes. For adults, BMI is categorized into four ranges and indicates varying levels of health risks. For Asians, BMI ranges are different. BMI below 18.5 indicates underweight, BMI range of 18.5-24.9 indicates a normal/healthy state, BMI range of 25-29.9 indicates overweight, and BMI equal to or higher than 30 is considered obese.

Obesity is, however, sub-classified as class I obesity (BMI of 30 to < 35), class II obesity (BMI of 35 to < 40), and class III obesity (BMI of 40 or higher). BMI for an individual is calculated by any of the following equations:

BMI = [weight (kg)/height (m)]

BMI = [weight (lb)/height (in)] * 703

Healthy metabolism is maintained through normal homeostasis and appropriate regulation of blood pressure, blood glucose and lipid profiles, etc. At the metabolic level, weight loss of % of initial weight is associated with improvement in biochemical and physiological parameters of the body and thus health benefits. Furthermore, weight loss programs are directed towards reducing weight by 1 to 2 pounds/week (approximately 0.5 to 1 kg/week). Recommended weight reduction prevents drastic changes in metabolism and is associated with better long-term weight maintenance.

Issues of Concern

Weight loss regimes usually depend on dietary modulations and calorie restrictions, exercise, and sometimes drug intervention or surgery. However, it is concerning that most people are unable to maintain the lost weight, and many regain a significant part of the lost weight. Notably, there are individual differences observed in weight maintenance. There is no standard effective regime developed thus far, and individual differences are observed in the manifestation of such regimes, and in some patients, it may not be successful. These differences in the positive outcome of weight loss management programs may be due to lifestyle choices, eating habits, and individual metabolic variations, besides not complying with the healthy diet.

Weight lost through calorie restrictions poses a risk of bone mobilization or bone loss. The combination of calorie restriction and exercise does not necessarily prevent or attenuate bone loss. Losing about % of body weight raises the risk for fractures, especially in older individuals. It requires a controlled weight-loss program design to pinpoint mechanisms adapted to support the quality and density of bone sites susceptible to bone loss. Hence, besides the clinical regime of weight loss from the point when it is initiated to achieving a healthy weight, management of lost weight also requires clinical support.

Weight loss through pharmacological and surgical interventions is becoming more appealing. Besides improving an individual's health and emotional status, they effectively reduce the risk factors for metabolic diseases. Nonetheless, they are associated with significant age-specific side effects. Surgical interventions such as sleeve gastrectomy usually lead to swift weight loss but are accompanied by changes in hormones, bone density, and gastrointestinal problems.

Weight regain after weight loss is also a frequent problem encountered in obesity. This tendency is often due to the lack of compliance to exercise or dietary regimes. However, in many cases, it occurs due to physiological mechanisms and not due to high-calorie intake or lack of exercise. Gut hormone secretions may lead to a reduced secretion of anorectic hormones and an enhanced orexigenic hormone affecting metabolic adaptation. This imbalance causes weight to be regained after weight loss has taken place. The BMI-induced metabolic shift may also lead to the weight regain process. Hence, it concerns that many central (metabolic) and peripheral (food craving, hunger sensation, and enjoyment of eating) mechanisms can cause regain of weight.

Enhancing Healthcare Team Outcomes

Unhealthy weight gain generally occurs through inducing and driving factors that perturb the metabolism, which may vary among individuals. Hence, the practitioners must recognize and evaluate the underlying causes and prescribe a regime for weight loss directed towards the specific causing and contributing factors to obtain desirable results. Furthermore, weight recidivism is observed at a high rate and thus requires a customized regime spanning metabolic effectors to maintain weight. This will involve a concerted effort from a multidisciplinary staff such as physicians, nutritionists, exercise physiologists, and trainers to recognize the potential causes and target their treatment strategies accordingly. Besides, weight reduction and regeneration of a healthy metabolism also depend on lifestyle, including healthy behavioral practices and eating habits. Thorough counseling of patients will warrant better patient outcomes. Weight management becomes more complex when it is a therapeutic pathway for health conditions such as type 2 diabetes, cardiovascular diseases, liver or kidney diseases, etc. The outcomes of such therapeutic intervention may depend on a carefully directed approach that prevents adverse side effects. However, to improve therapeutic outcomes, prompt consultation involving an interprofessional group of specialists is recommended.

Q/A - Metabolic Consequences of Weight Reduction

Q: What are the consequences of weight reduction on metabolism?

A: Weight reduction is associated with metabolic changes that have favorable effects on overall health. It can improve parameters such as blood pressure, blood glucose, lipid profiles, sleep apnea, and comorbidities.

Q: How can weight maintenance be achieved after weight loss?

A: Weight maintenance after weight loss requires equalized input and energy output to regulate optimal metabolism. This can be achieved through a balanced lifestyle, including healthy eating habits, exercise, and behavioral changes.

Q: What factors contribute to weight regain after weight loss?

A: Factors such as lack of compliance to exercise or dietary regimes, physiological mechanisms, gut hormone secretions, and the BMI-induced metabolic shift can contribute to weight regain after weight loss.

Q: What is the role of the healthcare team in weight management?

A: The healthcare team, including physicians, nutritionists, exercise physiologists, and trainers, plays a crucial role in recognizing and evaluating the underlying causes of unhealthy weight gain and prescribing customized regimes for weight loss. Thorough counseling and multidisciplinary collaboration are essential for successful outcomes.

Q: Are there effective pharmacological and surgical interventions for weight management?

A: There are some pharmacological and surgical interventions available for weight management, but they are associated with side effects and may not be universally effective. These interventions should be carefully considered and combined with lifestyle changes for optimal results.

Q: What are the metabolic hormones involved in weight loss and weight maintenance?

A: Metabolic hormones such as leptin, insulin, ghrelin, peptide YY, and others play a role in regulating energy intake, hunger, and satiety signals. Their concentrations can change during weight loss and maintenance, affecting weight regain.

Q: How does exercise impact metabolism and weight maintenance?

A: Exercise stimulates a negative energy balance, increases muscle mass, and improves insulin sensitivity and lipid profiles. It can help in weight maintenance by promoting an optimized body composition and increasing energy expenditure.

Q: What are the concerns with weight loss regimes?

A: Concerns with weight loss regimes include the inability to maintain the lost weight, bone loss, side effects of pharmacological and surgical interventions, and the high rate of weight regain. Individual differences and non-compliance can also affect the success of weight loss management programs.

Q: How does metabolic adaptation affect weight maintenance?

A: Metabolic adaptation is a process that occurs during weight loss and maintenance, leading to changes in enzyme functions, hormone concentrations, and energy expenditure. It can affect weight maintenance and the body's ability to resist weight modulation.

Q: What are the benefits of weight maintenance after weight loss?

A: Weight maintenance after weight loss has far-reaching benefits, including a general sense of well-being, more energy, reduction in stress levels, improved immunity, better mental health, balanced hormones, and an overall enhancement in the quality of social life.

Q: How can weight management be optimized for better outcomes?

A: Weight management can be optimized by recognizing and evaluating individual factors, prescribing customized regimes, promoting a balanced lifestyle, and ensuring the collaboration of a multidisciplinary healthcare team.