Scientists say a hormonal shift after dropping pounds can make maintenance an uphill battle.

The hardest part about weight loss might not actually be losing the weight — it’s fighting against your biology long after the initial pounds are lost.

A recent small study in the American Journal of Physiology-Endocrinology and Metabolism discovered that while both satiety and hunger hormones rise after weight loss, participants only reported greater overall hunger levels.

Researchers from the Norwegian University of Science and Technology, and other institutions, had 35 adults with severe obesity take part in a weight loss program that addressed diet and exercise. Over the course of two years, participants attended five three-week long sessions to learn about healthy weight loss methods, which they practiced throughout the study. Scientists recorded body weight and plasma concentrations of the participants’ hunger hormones and satiety hormones at four weeks, one year, and two years in the program.

All participants lost weight at each time period. At the one and two-year marks, participants had higher levels of hunger hormones and reported increased feelings of hunger. They also had higher levels of satiety hormones, but their feelings of fullness after eating a meal weren’t significantly changed after weight loss.

“Those who have lost weight with lifestyle interventions will need to deal with increased feelings of hunger in fasting for the rest of their lives if they are going to succeed,” said study co-author Catia Martins, PhD, an associate professor at the Norwegian University of Science and Technology.

It might seem odd that both hunger and satiety hormone levels increase after weight loss, but obese individuals have lower — not higher — concentrations of a hunger hormone called ghrelin when they’re in a fasting state, Martins said.

Since obese individuals have impaired secretion of some appetite-regulating hormones, after weight loss the levels likely rise because the body is trying to normalize to the levels typically seen in people of a healthy weight. This means their hunger hormones will also start to rise as their body works to regulate itself.

Once levels are normalized, this doesn’t necessarily mean your hunger hormones are doing battle with your satiety hormones to override them, though.

“It’s a much more complex circuitry,” said Dr. Amy Rothberg, a spokesperson for the Endocrine Society. Other hormones from the digestive system and leptin from fat sources also play a role in determining your senses of hunger and fullness, and that’s just one pathway that mediates the appetite control system.

“There are also motivational, cognitive, and emotional components to eating,” said Rothberg.

“Those are the systems that probably drive some of the subjective feelings of hunger,” she explained, noting that it can be hard to tease out real, physiological hunger from cravings.

Learning to be more in tune with the reasons for which you eat could help you consume less, she said.

While the research found that obese people who lost weight experienced greater feelings of hunger and an increase in ghrelin, they were still able to maintain their weight loss, said Martins.

Rothberg pointed out there are multiple ways for people to work to maintain their weight loss.

“People really can maintain their reduced weight by engaging in modifications to diet and increasing physical activity,” Rothberg explained. “Whatever those lifestyle modifications that got that person’s weight down, they need to stick with it.”

Just having the knowledge of how your body works and how it responds to weight loss can help to make more informed decisions about eating and staying active.

Hunger hormone levels rise in the evening and satiety hormone levels decrease in the evening, especially when stressed, found recent research in the International Journal of Obesity. That could set you up for a late night binge. But if you shorten your window of food consumption by eating earlier in the day and setting a time at which you stop eating for the day, you can avoid this behavior altogether, recommended Rothberg.

“We just have to change how we respond to our environment,” said Rothberg. That means constantly changing your strategies, whether it’s with distractions, avoidance, or other techniques that will help you limit food intake.

If you find yourself eating in the evenings as a response to stress, find another therapeutic avenue that will help you cope with that stress and keep yourself busy during those evening hours. Exercising, joining a club, or picking up a new hobby are all great distractions.

“With any behavior repeated over time, it can be habit forming,” Rothberg explained. “So just as our bad habits sunk in, we can make our new, good habits sink in, too.”