The Top Mistake People Make When Cutting Back on Calories

Many weight loss diets share a commonality: they restrict calories. After all, at the most basic level, your weight status is an equation of calories in, calories out. Research suggests that maintaining a calorie deficit (i.e., consuming fewer calories than you expend each day) is a primary factor in achieving weight loss. “Calorie restriction can be very effective for short-term weight loss,” says weight loss dietitian Melissa Mitri, M.S., RD. However, Mitri emphasizes that other factors, like the types of food you eat, a consistent exercise routine, and effective stress management strategies, are also crucial for maintaining long-term weight loss.

Effective as it may be, maintaining a calorie deficit can come with some common mistakes. The one Mitri says she sees most often: not consuming enough fiber. Neglecting this critical nutrient can do a surprising amount of harm to your weight loss efforts, not to mention derailing your digestion and downgrading your overall health. Here’s why dietitians say we often fall short of fiber when on a calorie-restricted diet and how you can ensure you’re getting enough. 

Why Fiber Falls By the Wayside When Trying to Lose Weight

Fiber Isn’t Exciting

Let’s be honest, in terms of popularity, fiber doesn’t hold a candle to other, glitzier nutrients like protein or dietary supplements. “One of the reasons people don’t get enough fiber is because they simply aren’t focused on it,” says weight loss dietitian Lainey Younkin, M.S., RD, LDN. “It doesn’t get as much attention as protein on social media.” Fiber’s longtime association with unsexy digestive habits could be to blame for its lack of pizzazz as a weight loss aid.

That said, fiber is a key nutrient for weight loss. Eating more of it is strongly associated with successful weight management, so it may be time to shift to a more balanced approach, prioritizing fiber along with other nutrients. Younkin says reading labels is a great place to start. “Look at the dietary fiber [on Nutrition Facts labels] to see how much is in various foods that you buy.”

The Focus Is On Protein

It’s no surprise that protein is all the rage at the moment. According to a 2025 survey by the International Food Information Council, 70% of Americans reported trying to consume more protein, a significant increase from 67% in 2023 and 59% in 2022. Additionally, high-protein diets have ranked as the most-followed eating pattern for the third consecutive year.

Protein is well and good, but it’s not the only superstar nutrient for weight loss. “There is so much emphasis on protein for weight loss from the media and influencers, which leads many to believe this is the only thing that matters,” Mitri says. “While protein is essential for health and certainly is one key nutrient for weight loss, fiber is just as essential to enhance fullness and provide volume on a reduced-calorie diet.” Not sure how much protein you need? Check out our protein calculator as a guide.

Overestimating Fiber Intake

If you eat a balanced diet, it’s easy to believe your fiber needs are taken care of. But that’s not necessarily the case. “[People often] assume that they’re getting enough from eating more fruits and vegetables, and while fruits and vegetables have fiber, you have to eat a lot of them to hit your daily fiber goal of 25-38 grams per day,” Younkin says.

 To do so, Younkin suggests varying your plate with whole grains, beans and legumes. And if you’re concerned about overdoing it on carbs, fear not! “I often find that clients are scared of carbs, but there’s no need to avoid them,” says Younkin. “It’s about choosing high-fiber carbohydrates and limiting refined carbohydrates. This will help you get more fiber, stay full longer and aid weight loss.”

Eating Too Few Calories

Sure, calorie restriction can be effective for weight loss, but taking it too far can mean overrestricting on fiber as well. “A lot of my clients often think the fewer calories they eat, the better, especially if they’ve followed very low-calorie or overly restrictive diets in the past,” Mitri says. On an extremely calorie-controlled diet, however, it can be hard to reach the recommended amounts of fiber. Each gram of fiber contains 4 calories. At the recommended 25 grams for women and 38 grams for men, this equates to just 100 and 152 calories, respectively, from fiber each day.

How to Eat Enough Fiber When Trying to Cut Calories

When pursuing weight loss, stick to these dietitian-recommended strategies to keep fiber high and calories low. 

• Prioritize protein and fiber. Both of these nutrients are important for staying full. “When planning your meals, ensure you have one to two quality sources of both protein and fiber, such as tuna or chicken for protein and leafy greens for fiber, which will help keep you full and thus make it easier to stick to a reduced-calorie diet,” Mitri advises.
• Keep variety in mind. You’ll find fiber in all sorts of foods, so don’t limit yourself to a mere handful of fruits and veggies. Whole grains, beans, nuts and seeds are other high-fiber choices.
• Incorporate favorite foods. If you’re not enjoying your diet, you’re less likely to stick with it. Mitri encourages keeping favorite foods on rotation, even when striving for a calorie deficit. Consider which high-fiber foods you genuinely like in your meals and snacks.
• Try a bigger, high-fiber breakfast. Younkin says the right breakfast can set you up for calorie-deficient success. “Instead of trying to eat less, eat enough of the right nutrients to keep you full and satisfied (protein, fiber and healthy fat), so you don’t raid the pantry later and end up in a calorie surplus.” Try adding high-fiber breakfast choices like oatmeal, bran cereal or a berry yogurt parfait.

Our Expert Take 

On a low-calorie diet, fiber is your friend. While it might not seem like the most impactful nutrient, it plays a major role in promoting satiation, curbing cravings and regulating digestion—all of which factor into the success of a weight loss program. As you dial down your calories, don’t fall prey to the mistake of neglecting fiber intake. High-fiber fruits, vegetables, whole grains, beans, nuts and seeds all deserve a place on a weight loss-friendly plate.