“Energy balance” is the relationship between “energy in” (food calories taken into the body through Yet a negative energy balance does lead to weight loss. Learn about energy balance and how it can help your family maintain a OUT supports natural growth without promoting excess weight gain. Body fat is an indicator of energy balance: Calories IN vs. you to gain 5 pounds of fat? ◦ days and obesity is a relationship between weight and height.
The few existing studies suggest that what appears to be a hazard associated with weight loss in observational studies is due to involuntary weight loss, and that losing weight voluntarily probably does not cause harm. For example, the Iowa Women's Health Study recently showed that intentional weight loss episodes of 9. Women with unintentional weight loss of 9.
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- Framing the Issue
- What is Energy Balance?
The surgery group had a far lower prevalence of diabetes compared with the diet group 8. Preliminary analyses also suggest lower mortality in the surgery group 33 In this study, greater amounts of weight loss were also associated with better quality of life The most common endpoints are alterations of blood pressure, lipid profile, and glucose tolerance, with only a few trials targeting clinical endpoints such as angina pectoris or myocardial infarction.
Most studies have been conducted among apparently healthy participants, although a few have been conducted among individuals with previous cardiovascular disease. In these studies, most participants achieved only slight to moderate alterations in weight.
Representative trials are presented in Table 2 Table 3 Table 4. Trials of weight loss and blood pressure. The effect of weight reduction on blood pressure has been examined in several trials.
Energy Balance and Obesity, Healthy Weight Basics, NHLBI, NIH
The Hypertension Control Program 36using a multifactorial approach CR, sodium and alcohol reductionshowed that a mean weight loss of 1. The Trials of Hypertension Prevention Phase I 37 assessed the effect of weight loss CR and increased physical activity on blood pressure among obese men and women aged 30 to 54 years with diastolic blood pressure DBP between 80 and 89 mm Hg.
After 18 months, mean weight loss was 4. The mean change in DBP for the intervention participants compared with controls was —2.
Managing weight is about more than energy balance or ‘bad foods’, warn experts
A similar result was obtained for systolic blood pressure SBP. Three trials compared separately the effects of weight loss and reduced sodium intake.
In the Trials of Hypertension Prevention Phase II 39intervention groups were successful in reducing blood pressure in the short term, though the intervention effect generally decreased with continued follow-up, except in the weight loss group.
At termination of the trial, blood pressure reductions remained higher in the weight-loss groups than in the usual-care group —1. The Trial of Nonpharmacologic Interventions in the Elderly 40 extended these findings to an elderly population. These studies clearly demonstrate the efficacy of weight loss and sodium restriction, alone or combined, in reducing blood pressure or in preventing development of hypertension. Trials of weight loss and lipid profile.
Previous trials have shown that weight reduction can improve lipid profiles. However, the comparative role of energy-restricted diets and physical activity—and their interaction—is still not clear, nor have the relative efficacies of reduced-fat diets and hypocaloric diets been established.
In the Stanford Weight Control Project I 41a one-year trial of overweight men aged 30 to 59 years, both exclusive dieters and exclusive exercisers lost significant amounts of weight: When compared with the control group, both intervention groups had significant increases in plasma concentrations of high-density lipoprotein cholesterol HDL-C and significant decreases in triglyceride levels, but levels of total and low-density lipoprotein cholesterol LDL-C were not significantly changed.
Thus, fat loss generated by either dieting or exercising produced comparable and favorable changes in HDL-C and triglycerides. This one-year trial assigned moderately overweight, sedentary men and women aged 25 to 49 years to one of three groups: Mean fat loss in the intervention groups ranged from 4.
The same research group addressed the impact of diet and exercise on people with dyslipidemia In a one-year trial, postmenopausal women and middle-aged men, all with moderate lipid alterations, were randomly assigned to aerobic exercise, an NCEP Step 2 diet, diet plus exercise, or to a control group that received no intervention. In women and men in both the diet and the diet-plus-exercise groups, intake of fat and cholesterol decreased significantly during the study, as did body weight.
In the exercise-only group and in the controls, neither dietary intake nor body weight decreased. Changes in HDL-C and triglyceride levels did not differ significantly among the treatment groups for subjects of either sex.
In the diet-plus-exercise group, serum LDL-C levels were significantly reduced among women — The reduction in LDL-C in men in the diet-plus-exercise group was also significant compared with the reduction among men in the exercise-only group —3. In contrast, the observed reductions in LDL-C levels in the diet-only group were not statistically significant among the women —7.
Because the NCEP step 2 diet failed to lower LDL-C levels in men or women with high-risk lipoprotein levels who did not engage in aerobic exercise, this finding highlights the importance of physical activity in the treatment of elevated LDL-C levels. One possible conclusion is that losing weight is important in reducing LDL-C, independent of increased physical activity, for overweight men and postmenopausal women. For those with moderately elevated cholesterol levels, however, physical activity appears to be an important adjunct to a reduced-fat diet for increasing levels of HDL-C and reducing LDL-C.
The relative contributions of weight loss and aerobic exercise in reducing insulin resistance were compared in a trial 44 of healthy, sedentary, obese, middle-aged and older men who were randomly assigned to a 9-month diet-induced weight loss intervention, a 9-month aerobic exercise training program, or weight maintenance. Other similar trials have shown comparable findings.
A trial conducted in Da Qing, China, randomized men and women with impaired glucose tolerance from 33 clinics into a control group, a diet-only group, an exercise-only group, and a diet-plus-exercise group.
Randomization was conducted by clinic. Trials of weight loss among persons with previous CHD. Several trials have been designed to test the association between weight loss, other lifestyle factors, and coronary atherosclerosis progression and clinical events among patients with CHD. The Stanford Coronary Risk Intervention Project 46 compared usual care with a multifactorial risk reduction approach diet low in fat and cholesterol, exercise, weight loss, smoking cessation, and medications to favorably alter lipoprotein profile among patients with atherosclerotic lesions defined by coronary angiography.
Clinical cardiac events led to 25 hospitalizations in the risk-reduction group compared with 44 in the usual-care group relative risk [RR], 0.
In the Lifestyle Heart Trial 47 48performed among patients with angiography-defined coronary atherosclerosis, an experimental group low-fat vegetarian diet, smoking cessation, stress management training, and moderate exercise was compared with a usual-care control group for a one-year period. On average, coronary stenosis diameter regressed from Twenty-five cardiac events occurred in 28 experimental-group patients compared with 45 events in 20 control group patients during the 5-year follow-up RR for the control group was 2.
These multifactorial trials were unable to assess the independent effect of weight loss or of other isolated lifestyle modifications and so have limited relevance for this panel. Feasibility of Sustained CR for Weight Loss and Subsequent Maintenance Given the current state of knowledge, is it feasible for humans to reduce their caloric intake over the long term?
Several issues should be considered in answering this question. First, it is extremely difficult to get accurate assessments of dietary intake.
Thus, a better answer to this question comes from studies that have asked participants to lose weight and maintain it, where weight is an objective measure. Such interventions, however, typically include not only CR but also increased exercise; as will be discussed, it appears that those who are successful at long-term weight loss use a combination of these strategies.
Whether it is the combination of dietary restriction and increased exercise that is physiologically important, or whether adherence to both represents a marker of relatively heightened motivation and adherence to caloric restraint is unclear.
Nevertheless, it does seem that those who adhere closely to both diet and exercise prescriptions do better in weight loss programs. Second, it should be noted that such data have been obtained on overweight participants who are intentionally attempting to lose weight. It is unclear whether similar effects would be observed in normal-weight persons. Several large-scale hypertension trials have included weight loss as one of the interventions and carried out long-term follow-up.
The obese participants mean BMI of 30 in men, The intervention goal was to achieve and maintain a 4. The intervention included weekly meetings for an initial 4 months, biweekly meetings for the next 4 months, and monthly thereafter.
Subjects assigned to the weight loss-alone arm or the combined weight loss-plus-sodium restriction arm achieved a mean weight loss of 5 kg 11 lb at 6 months and maintained this through month Subjects in the group assigned to the weight loss-alone group lost approximately 1 kg 2. Similar positive long-term results for weight loss have been obtained in other hypertension clinical trials.
For example, in the Treatment of Mild Hypertension Study, participants aged 45 to 69 participated in a weight-loss intervention while also receiving antihypertensive medication or placebo. The intervention involved 6 months of intensive treatment, with a combination of group and individual sessions, and then individual sessions every 6—12 weeks for the remainder of the trial.
Participants lost a mean of 4. In the Trials of Hypertension Prevention, the weight loss intervention group lost a mean of 3. No adverse effects of weight loss have been observed in any of these trials. Based on these as well as other trial data, it appears that weight loss can be achieved and maintained, at least over the short term on the order of 1 to 3 years.
When energy intake exceeds energy expenditure, a state of positive energy balance occurs and the consequence is an increase in body mass, of which 60 to 80 percent is usually body fat 2. Conversely, when energy expenditure exceeds energy intake, a state of negative energy balance ensues and the consequence is a loss of body mass again with 60 to 80 percent from body fat. Any genetic or environmental factor that impacts body weight must act through one or more component of energy balance.
How the Body Achieves Energy Balance Our understanding of the mechanisms by which the body acts to achieve and maintain energy balance is incomplete, but the available evidence suggests that a complex physiological control system is involved.
This system includes afferent signals from the periphery about the state of energy stores and efferent signals that affect energy intake and expenditure 3. Furthermore, we know that the components of energy balance can be influenced by changes in each other as a consequence of positive or negative energy balance 4 - 10which act to defend body energy stores, maintain energy balance and preventing shifts in body mass.
If energy balance was not controlled by such a system and were subject only to behavioral mechanisms controlling food intake and volitional energy expenditure most people would routinely experience wide swings in body weight over short periods of time. The relative stability of body weight from day to day is consistent with the view that energy balance is subject to physiological control. In practical terms, assessment of energy balance is usually accomplished by assessment of body weight or body composition to estimate total energy content.
Energy balance itself, is not something that is measured, but rather various surrogates are measured that represent the sum total of energy inputs and outputs and the state of body energy stores. However, we do not have the ability to measure the small changes in energy balance that could impact body weight. Given this, great care should be taken in making predictions about changes in body weight from measures of either energy intake or energy expenditure. Obesity is not a Problem in only one Component of Energy Balance Despite the evidence for a control system, most people in today's environment gain significant escess body weight and body fat over their adult years.
This does not argue against an energy balance control system, but suggests there may be limits to the body's ability to match intake and expenditure under the prevailing conditions in the modern environment. For example, one can develop some crude estimates of the extent to which food intake has increased and physical activity has decreased over the past decades. With no active regulation or adaptation of energy balance, this increase theoretically could explain a yearly weight gain of 18 pounds for men and 35 pounds for women.
On the energy expenditure side, Basset et al 12 examined physical activity patterns in an Old Order Amish population who are living an agrarian lifestyle typical of a large fraction of the population in the U. Using pedometers, they found that Amish men walked an average of about 18, steps per day and women an average of about 14, per day.
Basset et al 13 also reported that inthe average American adult walked about 5, steps per day. Without taking account of physiological adaptation, this decline in physical activity over the past century could explain a yearly weight gain of 68 pounds for men and 47 pounds for women. Similarly Church et al. This alone could explain a substantial amount of weight gain in the population. Although these estimates are crude, the point is that taken together, the changes in reported energy intake and energy expenditure over the past decades would predict more weight gain by fold in adults than actually has occurred if there were not some physiological processes attempting to maintain energy balance.
Further, because alterations in one component of energy balance affect the others 4 - 10it is not realistic or helpful to attribute obesity solely to energy intake or energy expenditure. A great example of the way that components of energy balance interact is demonstrated by Hall et al. They showed that the traditional estimate of a pound of weight loss with each kcal of negative energy balance was not true because of reductions in energy expenditure in response to decreases in energy intake, and that the actual weight loss would be less than expected.
Managing weight is about more than energy balance or ‘bad foods’, warn experts
The same would hold true for weight gain — the expected weight gain would be less than predicted from the degree of positive energy balance because of the interaction among components of energy balance. Theoretically, an individual can achieve energy balance in multiple ways. Energy balance can be achieved at different levels of body weight and body composition and it can be achieved at different levels of energy intake and energy expenditure as long as the two are equal over a period of time.
However, the way energy balance is achieved may be affected by characteristics of human physiology. Based on our review of the energy balance literature and information about how our modern lifestyle differs from decades ago, we hypothesize that human physiology developed under circumstances that conferred a advantage for achieving energy balance at a relatively high compared to resting metabolic rate level of energy expenditure--a high energy throughput—or high energy flux.
The idea that energy balance is best regulated at high but not excessive levels of physical activity was first proposed by Jean Mayer and colleagues in the s Mayer observed that energy intake was better matched to energy expenditure when people were physically active.
While these studies in man were cross sectional in nature, other prospective studies published by Mayer and colleagues conducted in rats established the linearity of coupling between food intake and energy expenditure only within certain limits