You've probably heard fitness influencers talk about a calorie deficit and, while burning more calories than you consume is not a new weight loss method, it is certainly something many Americans will aim to do this year.
According to CDC data, one in five adults (20%) in each U.S. state is living with obesity. So, it is no surprise that almost half of American adults say starting a new diet is one of their New Year's resolutions, according to a new Physicians Committee for Responsible Medicine/Morning Consult survey.
The poll of 2,174 men and women found that 40 percent plan to attempt eating fewer calories in 2025. When combined with exercise and a healthier diet, this approach can work wonders.
Newsweek spoke to multiple experts in nutrition and sports to identify the top five mistakes to avoid when in a calorie deficit.
How To Calculate a Calorie Deficit
The 2020-2025 Dietary Guidelines for Americans state that female adults require between 1,600 to 2,400 and males from 2,000 to 3,000 calories per day. A number of factors determine how much one should consume, such as physical activity, illnesses, gender and environmental factors.
But to be in a deficit, one must safely drop their calories. To do this, sports nutrition brand Myprotein recommends you start by calculating your daily calorie needs to determine your basal metabolic rate, which is the number of calories your body needs at rest.
Then factor in your activity level (from sedentary to very active) to estimate your total daily energy expenditure (TDEE)—the calories needed to maintain your current weight. To lose weight, create a calorie deficit by eating fewer calories than your TDEE, aiming for a gradual, sustainable weight loss of 0.5kg to 1kg per week.
Five Things Not To Do in a Calorie Deficit
Wade Lightheart, a certified sports nutrition adviser and president of BIOptimizers, based in Vancouver, British Columbia, and Gillian Killiner, a registered dietitian from England with over 30 years of experience in nutrition, shared their insights.
1. Avoid Extreme Calorie Cuts
"Even though your goal is to be in a caloric deficit, don't go too extreme," said Lightheart.
Killiner added, "Drastic reductions can cause nutrient deficiencies, hormonal imbalances and slower metabolism, making sustained weight loss difficult."
2. Prioritize Rest and High-Quality Sleep
In 2010, researchers from the University of Chicago, Illinois, conducted a study showing that sleep plays a critical role in weight loss. Over two weeks of calorie restriction, participants who slept 8.5 hours per night lost significantly more fat (1.4 kg) than those who slept only 5.5 hours (0.6 kg). The short-sleep group also lost more muscle mass (2.4 kg vs. 1.5 kg).
Shorter sleep increases hunger, alters metabolic hormones and reduces the body's ability to burn fat. These findings highlight the importance of sufficient sleep for effective fat loss, muscle preservation and hunger management during dieting.
3. Don't Overdo It in the Gym
Lightheart explained, "You may think training harder means more weight loss, but that's not necessarily true. Excessive exercise can trigger metabolic stress, making weight loss more challenging because you've activated your body's stress response. This can lead to increased cortisol levels, muscle breakdown and a slower metabolism."
4. Don't Skip Meals
Killiner told Newsweek: "Skipping meals can lead to blood sugar fluctuations, increased hunger, cravings and overeating later."
5. Never Neglect Hydration
"Dehydration can mask hunger feelings and affect digestion," Killiner said. "Hydration is vital for energy levels during weight loss."
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