Experts always talk about eating in a calorie deficit to lose weight, but dipping too low can also be an issue. Without enough food for survival (including our normal daily functions), your body will send signals to conserve calories, slowing down your metabolism, explained registered dietitian Lisa Bunn, CSCS. "While calorie deficit is a must for weight loss, the nuance is that we don't want it to be too much of a deficit."

Lisa explained that without enough food for survival, our bodies will start shutting down and use muscle tissue for energy instead of fat stores. Aim for a moderate calorie deficit, not a major one, to avoid extreme hunger, which could result in binge eating. When creating a calorie deficit, never dip below 1,200 calories a day.

The difference between being in a calorie deficit and a calorie surplus (losing vs. gaining weight) can be a few hundred calories, Lisa explained, so she recommends tracking food to accurately calculate what you're eating.

When using running as a tool to decrease your overall body fat percentage, and therefore reduce belly fat, it's essential to eat a balanced diet. Focus on whole foods, including complex carbs like whole grains, adequate protein, and healthy fats at consistent times throughout the day, recommended Jessica. She said that keeping a food journal can help you lose weight because it can help you identify when you may mindlessly snack or eat extra calories — all those handfuls of M&Ms add up!

If you're eating tons of added sugar and refined carbs, it's not necessarily the empty calories you need to worry about that leads to weight gain. Jason Fung, MD, a nephrologist, explained in a previous interview that eating processed carbs and sugary foods such as doughnuts, crackers, pasta, white bread, and alcohol spikes your insulin levels, which can cause weight gain. Keeping your insulin levels low will help reduce your overall body fat percentage, and that includes belly fat.

The issue may be that you're just not running enough. ACE-certified personal trainer Rachel MacPherson from Radical Strength said to begin with 20- to 30-minute runs at a comfortable pace every other day, gradually working up to 45-minute runs.

ACE-certified trainer Amanda Brooks said in a previous interview that "running 20 to 30 miles per week is plenty for someone looking to lose weight and improve overall health."

If you're spending a lot of time doing steady-state cardio, or too much cardio, you can end up making too much cortisol, a stress hormone, which can contribute to belly fat, Rocio Salas-Whalen, MD, board-certified endocrinologist at New York Endocrinology explained in a previous interview.

NASM-certified trainer Adam Padgett added that if your results have stalled, skip the long slow runs and do HIIT cardio. "This will push your body to increase metabolic rate and accentuate weight loss," he said. Adding in hills and sprints is an effective way to run for weight loss. Here's a 30-minute HIIT running workout you can try.

Instead of focusing on more cardio, incorporate strength training three times a week to build more calorie-burning muscle mass. Although you can't spot reduce fat from your belly with a million crunches, Krissi recommends doing ab-based exercises like dead bugs, planks, side bridges, pallof presses, and hollow holds.

"These exercises will help your abs engage in a way that will support other strength training exercises such as compound lifts like squats, deadlifts, or bench presses, which you should also do in your strength program," Krissi said.

You're Stressed Out

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"Belly fat itself is a different beast. If you find you are able to lose weight in other places but not your belly, the culprit could be genetics, but it also could be cortisol," explained Rachel. If you have a fast-paced, busy life (you're not alone!), the level of stress hormones in the body will rise. Then you go running and this also creates high levels of cortisol levels in the body, explained NASM-certified trainer Ondrea Lynn. "They go back into their life after their run and repeat the stress cycle."

Increased cortisol levels can cause your body to hang on to fat on your tummy more than on other places. That's because "over time, persistently high levels of cortisol seen in stress promote the storage of excess glucose as fat in the abdomen, causing belly fat," Erica Patel, MD, explained in a previous interview.

Find ways to lower your stress levels and take a little time for self-care: read, listen to music, take a bath, meditate, write in a journal, or spend time with friends and family that lift your mood.

Running Isn't Your Thing

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"Just as one diet doesn't work for everyone, one exercise plan doesn't work for everyone," said ACE-certified trainer Sara Haley. "Running may not be what your body needs for weight loss." She recommended trying out different forms of cardio and mixing it up — try biking, boxing, hiking, cycling, CrossFit, or swimming — something you enjoy, that you'll stick with consistently.