https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5764193/

Synopsis

Weight loss can be achieved through a variety of modalities, but long-term maintenance of lost weight is much more challenging. Obesity interventions typically result in early rapid weight loss followed by a weight plateau and progressive regain. This review describes our current understanding of the biological, behavioral, and environmental factors driving this near-ubiquitous body weight trajectory and the implications for long-term weight management. Treatment of obesity requires ongoing clinical attention and weight maintenance-specific counseling to support sustainable healthful behaviors and positive weight regulation.

Keywords: obesity treatment, weight loss, weight maintenance, behavioral counseling, appetite, physiology

Introduction

Robert is a 47 year old patient who initially weighed 270 pounds. He lost 85 pounds three years ago by carefully following your guidance to decrease his caloric intake to 1500 calories per day and exercise six days weekly. Today he comes in for his annual physical examination. You were excited to hear about his continued progress and see how much more he’s lost, but you felt immediately dejected to see that he had regained almost 60 pounds. “I don’t know what to do…the weight keeps coming back on. I keep trying, but there must be something wrong. I’m sure my metabolism is in the dumps. It feels like every moment of the day I can’t help but think about food – it was never like this before I lost the weight. And no matter how hard I try to stop eating after one serving, I just can’t seem to do it anymore.” Feeling defeated, he says “I don’t even know what’s the point of doing this anymore!”

Frustrated, you remind him that he was able to do it just fine when he was losing weight initially, and he just needs to keep working hard at it. “I know it’s not easy, but I can’t help you unless you’re willing to help yourself. You just need to work harder and take control of this again.” You feel for him, but you know that you need to be stern to get him past this backsliding. Hoping to motivate him, you remind him how bad he will feel if he regains more weight, and you tell him to make a follow-up appointment for six months and warn him that if he doesn’t turn things around quickly he will have to restart his blood pressure medications.

Substantial weight loss is possible across a range of treatment modalities, but long-term sustenance of lost weight is much more challenging, and weight regain is typical1–3. In a meta-analysis of 29 long-term weight loss studies, more than half of the lost weight was regained within two years, and by five years more than 80% of lost weight was regained (Figure 1)4. Indeed, previous failed attempts at achieving durable weight loss may have contributed to the recent decrease in the percentage of people with obesity who are trying to lose weight5 and many now believe that weight loss is a futile endeavor6.

Here, we describe our current understanding of the factors contributing to weight gain, physiological responses that resist weight loss, behavioral correlates of successful maintenance of lost weight, as well as the implications and recommendations for long-term clinical management of patients with obesity.

Why is it so difficult to lose weight and keep it off?

The obesogenic environment

Long term weight management is extremely challenging due to interactions between our biology, behavior, and the obesogenic environment. The rise in obesity prevalence over the past several decades has been mirrored by industrialization of the food system7 involving increased production and marketing of inexpensive, highly-processed foods8–10 with supernormal appetitive properties11,12. Ultraprocessed foods13 now contribute the majority of calories consumed in America14 and their overconsumption has been implicated as a causative factor in weight gain15. Such foods are typically more calorically dense and far less healthy than unprocessed foods such as fruits, vegetables, and fish16. Food has progressively become cheaper17, fewer people prepare meals at home18,19, and more food is consumed in restaurants18. In addition, changes in the physical activity environment have made it more challenging to be active throughout the day. Occupations have become more sedentary20 and suburban sprawl necessitates vehicular transportation rather than walking to work or school as had been common in the past. Taken together, changes in the food and physical activity environments tend to drive individuals towards increased intake, decreased activity, and ultimately weight gain.

Physiological responses to weight loss

Outdated guidance to physicians and their patients gives the mistaken impression that relatively modest diet changes will consistently and progressively result in substantial weight loss at rate of one pound for every 3500 kcal of accumulated dietary calorie deficit21–24. For example, cutting just a couple of cans of soda (~300 kcal) from one’s daily diet was thought to lead to about 30 pounds of weight loss in a year, 60 pounds in 2 years, etc. Failure to achieve and maintain substantial weight loss over the long term is then simply attributed to poor adherence to the prescribed lifestyle changes, thereby potentially further stigmatizing the patient as lacking in willpower, motivation, or fortitude to lose weight25.

We now know that the simple calculations underlying the old weight loss guidelines are fatally flawed because they fail to consider declining energy expenditure with weight loss26. More realistic calculations of expected weight loss for a given change in energy intake or physical activity are provided by a web-based tool called NIH Body Weight Planner (http://BWplanner.niddk.nih.gov) that uses a mathematical model to account for dynamic changes in human energy balance27.

In addition to adaptations in energy expenditure with weight loss, body weight is regulated by negative feedback circuits that influence food intake28,29. Weight loss is accompanied by persistent endocrine adaptations30 that increase appetite and decrease satiety31 thereby resisting continued weight loss and conspiring against long-term weight maintenance.

Explaining the weight plateau

The overlapping physiological changes that occur with weight loss help explain the near-ubiquitous weight loss time course: early rapid weight loss that stalls after several months, followed by progressive weight regain32. Different interventions result in varying degrees of weight loss and regain, but the overall time courses are similar. As people progressively lose more and more weight, they fight an increasing battle against the biological responses that oppose further weight loss.

Appetite changes likely play a more important role than slowing metabolism in explaining the weight loss plateau since the feedback circuit controlling long-term calorie intake has greater overall strength than the feedback circuit controlling calorie expenditure. Specifically, it has been estimated that for each kilogram of lost weight, calorie expenditure decreases by about 20–30 kcal/d whereas appetite increases by about 100 kcal/d above the baseline level prior to weight loss31. Despite these predictable physiologic phenomena, the typical response of the patient is to blame themselves as lazy or lacking in willpower, sentiments that are often reinforced by healthcare providers, as in the example of Robert, above.

Using a validated mathematical model of human energy balance dynamics27,31, Figure 2 illustrates the energy balance dynamics underlying the weight loss time courses of two example 90 kg women who either regain (blue curves) or maintain (orange curves) much of their lost weight after reaching a plateau within the first year of a diet intervention. In both women, large decreases in calorie intake at the start of the intervention result in rapid loss of weight and body fat leading to a modest decrease in calorie expenditure that contributes to slowing weight loss. However, the exponential rise in calorie intake from its initially reduced value is the primary factor that halts weight loss within the first year. In contrast to the modest drop in calorie expenditure of less than 200 kcal/d at the weight plateau, appetite has risen by 400–600 kcal/d and energy intake has increased by 600–700 kcal/d since the start of the intervention.

These mathematical model results contrast with patients’ reports of eating approximately the same diet after the weight plateau that was previously successful during the initial phases of weight loss33. While self-reported diet measurements are notoriously inaccurate and imprecise34–36, it may be possible to reconcile such data with objectively quantified increases in calorie intake. It is entirely possible that patients truly believe they are sticking with their diet despite not losing any more weight or even regaining weight.

The patient’s perception of ongoing diet maintenance despite no further weight loss may arise because the physiological regulation of appetite occurs in brain regions that operate below the patient’s conscious awareness37. Thus, signals to the brain that increase appetite with weight loss could introduce subconscious biases such as portion sizes creeping upwards over time. Such a slow drift upwards in energy intake would be difficult to detect given the large 20–30% fluctuations in energy intake from day to day38,39. Furthermore, a relatively persistent effort is required to avoid overeating to match the increased appetite that grows in proportion to the weight lost31. For example, the model-calculated intervention effort for the simulated patient who experiences the weight plateau at six months followed by weight regain (Figure 2, blue curves) maintains more than ~70% of their initial intervention effort until the plateau. Perhaps self-reported diet maintenance before and after the weight plateau is more representative of the patients’ relatively persistent effort to avoid overeating in response to their increased appetite31. New technologies using repeated weight monitoring can be used calculate changes in calorie intake and effort over time40 and help guide individuals participating in a weight loss intervention41–44.