Weight loss interventions that work: Lifestyle changes

"If you really want to keep weight off, it requires permanent lifestyle changes. ... There are no quick fixes," said Mascha Davis, a registered dietitian and national spokeswoman for the Academy of Nutrition and Dietetics. "Otherwise, the weight loss is temporary, and you can gain it back when you go back to old habits."

To get started on your weight loss journey, Davis recommends looking at three areas of your lifestyle that might require change: food, exercise and sleep. "I call it a trifecta approach, because these three things are essential to keeping weight loss sustainable," she said.

For example, in the diet category, you might start eating more fiber-rich vegetables and aim to drink more water. Being more physically active might involve simply getting up every hour if you have a desk job, taking the stairs instead of the elevator and parking your car farther from an entrance.

Going to the gym regularly is helpful, but don't expect it to make up for those morning doughnuts. Generally speaking, the amount of exercise required to make up for diet damage is huge (think of walking briskly for nearly two hours to burn off a 500-calorie piece of cake) and explains why diet is generally more crucial than exercise for weight loss.

Since sleep impacts hunger and satiety hormones, getting enough Zs is another lifestyle factor that can make or break your weight loss efforts.

"Sleep is essential for weight loss," Davis said. "I have clients who are doing all these great things with their eating habits and going to the gym, but they don't realize that a lack of sleep is really wrecking their goals."

If you're constantly tired and drinking coffee all day, you may need to make some adjustments. "Most adults need seven to eight hours of sleep ... and some need as many as nine. A lot of people are walking around sleep-deprived -- but the less sleep you get, the higher your weight tends to be," Davis said.

If you're not seeing any results after a couple of months, meeting with a professional who is aware of your health history and can personalize a plan based on your habits and food preferences can be extremely helpful. For those with medical conditions, it's especially important to avoid fad diets or diets that eliminate food groups and seek the expertise of an experienced registered dietitian.

"Cutting out carbohydrates can be dangerous for someone with diabetes, but they may not even realize the potential harm," Davis said. Similarly, someone with chronic kidney disease may have to limit the amount of protein they eat and would need to steer clear of diets that promote a high intake of protein.

Implementing behavior changes and strategies to help you achieve your goals can be very helpful. For example, setting mini-goals that are specific and measured on a weekly basis -- such as taking a daily 15-minute walk during a lunch break -- can help take a lofty weight loss goal and break it down into something much more achievable.

Focusing on intuitive eating can be another important behavior change. It involves getting in touch with your body's hunger and satiety signals and figuring out how to nourish yourself without feeling deprived, Davis explained.

For many, the simple notion of just "eating less and moving more" in order to lose weight might seem oversimplified -- and extremely difficult. In fact, there is a physiological basis for why it is so hard. Once we lose even a small amount of weight by cutting back on calories, our body fights to defend our "original" weight, in part by decreasing our metabolism and increasing appetite. This can lead to frustration and the desire to give up, which can cause us to regain the weight we've lost, plus more, despite our best intentions.

If you are unable to lose weight or to continue losing after an initial loss despite making changes to your diet, exercise and sleep habits, and you've ruled out other possible causes that might prevent weight loss, such as hypothyroidism or Cushing's syndrome or prescriptions associated with weight gain, it might be time to consider a weight loss medication.