Whether you're shedding pounds aided by potent new medications, slimming down post-weight loss surgery, or reducing calories while increasing physical activity, there will come a moment when the digits on the scale cease their descent, marking the arrival of the dreaded weight loss plateau.
In a recent investigation, Kevin Hall, a scientist at the National Institutes of Health specializing in metabolic measurement and weight alteration, examined the point at which weight loss typically halts depending on the method employed. He dissected this plateau into mathematical models, drawing from robust clinical trial data encompassing various weight loss strategies, aiming to unravel the reasons behind this cessation. The findings of this study were published Monday in the journal Obesity.
Hall discovered that one contributing factor to the effectiveness of gastric bypass surgery and novel weight loss medications like Wegovy and Zepbound is their ability to extend the duration before hitting a plateau. Individuals can sustain weight loss for a longer period compared to solely reducing calorie intake.
The body regulates weight by striving to maintain a balance between calorie intake and expenditure. As we reduce calories or increase physical activity, tapping into our stored energy, appetite surges, prompting us to consume more. Hall's research demonstrates that as individuals shed more weight, appetite intensifies, sometimes nullifying all their efforts to lose weight.
This feedback loop was advantageous for our ancestors who hunted and gathered for survival, but it proves less effective for modern humans surrounded by readily available, energy-dense, ultra-processed foods.
Plateaus at different points
To explore the trajectory of weight loss through calorie restriction alone, Hall analyzed the weight fluctuations observed in the CALERIE study. This study, conducted from 2007 to 2010 and sponsored by the NIH, randomly assigned 238 adults to either adhere to a 25% calorie-restricted diet for two years or maintain their regular eating habits. Participants in the calorie-restriction group, on average, shed about 16 pounds, while those in the control group gained roughly 2 pounds.
Despite the participants' sustained efforts over two years, their weight loss plateaued around the 12-month mark as their appetites surged to counteract it.
Hall emphasizes that his study deals with averages and that the timing of a weight loss plateau may differ among individuals.
According to Hall's model, to achieve the reported weight loss in the CALERIE study, individuals who initially consumed 2,500 calories per day needed to reduce their intake by just over 800 calories daily. In response, their bodies urged them to consume an additional estimated 83 calories for every kilogram of weight lost.
For every 2.2 pounds lost, participants experienced a demand for 83 more calories per day. Despite feeling the need for an extra 622 calories daily at their lowest weights, they weren't actually consuming that amount. Instead, it reflected the increased appetite they experienced while exerting the same effort to cut 800 calories daily.
By the study's conclusion, participants found themselves exerting similar efforts as they did initially to resist food, but only managing to cut about 200 calories daily instead of the targeted 800, leading to a cessation in weight loss.
Dr. Christopher Gardner, director of nutrition studies at the Stanford Prevention Research Center, previously explained to CNN the feedback mechanism behind the increasing difficulty of weight loss with further reduction.
As per Hall's model, as participants in the CALERIE study shed more weight, their appetites resurged, causing them to reach a weight loss plateau around the 12-month mark.
The medications semaglutide and tirzepatide, which mimic gut hormones to aid in weight loss, induced greater dietary restriction. According to Hall's model, as individuals gradually escalated their dosage during the trial, they transitioned from consuming approximately 600 fewer calories per day to a reduction of 1,300 calories per day at the highest dosage for semaglutide, the active ingredient in Wegovy. For tirzepatide, the compound found in Zepbound, the calorie deficit increased from 830 on the lowest dosage to 1,560 on the highest dosage assessed in the study.
However, significantly, the medications didn't solely impact the quantity of calories individuals trimmed from their diets. They also diminished the number of calories their bodies prompted them to consume as they shed pounds—essentially dampening their appetites. With Wegovy, individuals desired to consume only about 49 calories daily for every kilogram of weight they lost. For Zepbound, this figure was 48. By halving their appetites, they managed to sustain weight loss for a more extended period, an additional year on average compared to solely calorie restriction. Typically, individuals taking weight loss medications ceased losing weight around the two-year mark.
Weight loss surgery yielded the most substantial effect, compelling individuals to slash approximately 3,600 calories from their daily intake, and only ingest back 58 calories for every kilogram they lost per day. Those who underwent weight loss surgery also experienced an additional year before reaching their weight plateau, suggesting that the surgery significantly decreased their appetite.
More interventions might be necessary
Hall underscores several key insights from this study. Initially, he highlights that medications like Wegovy and Zepbound, as well as interventions such as weight loss surgery, extend the duration before hitting a plateau, albeit not preventing it entirely.
"What's occurring is they still encounter an escalation in appetite as they lose more weight," Hall explains.
"If there were no appetite feedback loop, essentially, if the drug simply took effect and their intake remained at an extremely low level, it would require many years for them to reach a plateau, resulting in an excessive weight loss," Hall elaborates.
While it may impede individuals striving to lose weight, Hall emphasizes that the appetite feedback loop is, in fact, beneficial. It would be perilous if a drug or treatment eliminated appetite altogether, potentially leading to starvation.
Furthermore, Hall suggests that the study refines certain notions regarding why weight loss plateaus occur.
For instance, a prevailing theory posits that weight loss adversely affects metabolism, causing individuals to burn significantly fewer calories at rest compared to their initial state, thus facilitating weight regain.
Hall acknowledges that metabolism does decline post-weight loss, "but not to the extent required to account for the timing or magnitude of the weight loss plateau," he remarks.
Moreover, Hall contends that the study appears to debunk the idea that the efficacy of drugs diminishes over time. "I believe that notion is also inaccurate," Hall states.
"Our modeling indicates that the plateau occurs because the drug's impact is countered by the increase in appetite," he clarifies.
At times, individuals hit a plateau well before attaining their target weight, which can be highly frustrating.
In such scenarios, Hall suggests incorporating additional interventions to enhance their efficacy.
"Another common approach now is for individuals who didn't achieve the desired weight loss from bariatric surgery to supplement with one of the GLP-1 receptor agonists, thereby layering interventions," Hall explains.
Regardless of the chosen approach, Hall stresses that sustaining the weight loss necessitates persistent effort. Therefore, it's essential to assess whether one can maintain the chosen lifestyle intervention in the long term.
For individuals encountering a plateau after reducing calorie intake, breaking through it may entail further calorie restriction or integrating exercise into their routine.
"The key here is consistency. Whatever approach you adopt, you must continue it. You need to be content with that lifestyle intervention for the remainder of your life; otherwise, it won't yield the desired benefits," Hall concludes.
