Low-carb diets can deliver quick weight loss and energy, but early benefits often fade.Cutting carbs long term may cause fatigue, nutrient gaps, cravings and digestive issues.A balanced diet with fiber-rich carbs, protein and healthy fats is more sustainable.
Whether your goal is weight loss, more energy, fewer cravings or better blood sugar control, you’ve probably heard that a low-carb diet is the answer. While going low-carb can offer benefits for some people, it isn’t the best fit for everyone.
The first few weeks of cutting back on carbohydrates can feel surprisingly good—but that “honeymoon” phase doesn’t always last. Over time, some people notice fatigue, digestive changes, stronger cravings or difficulty maintaining strict carb limits.
We spoke with nutrition experts to explain why low-carb diets can initially feel great but are often short-lived—and what a more sustainable approach may look like instead.
Why You May Feel Great on a Low-Carb Diet
Many people feel great when they first cut back on carbs because their overall diet quality often improves. “When people first make this shift, they often replace more processed foods with nutrient-dense options such as vegetables, proteins and healthy fats,” says Juliana Crimi, RD, M.H.Sc. That change can mean fewer overall calories and more protein, which can make meals feel more satisfying and may reduce the urge to graze between them.
Those early shifts often make a difference on the scale, which can feel encouraging if weight loss is one of your goals. But much of that initial drop isn’t completely body fat. “Low-carb diets often lead to rapid early weight loss due to glycogen depletion and associated water loss, not fat loss,” says Karolin Saweres, M.S., RDN, LD. As the body uses up stored glycogen, it releases water along with it, causing the scale to move quickly—even before meaningful fat loss occurs.
Some people also notice improved energy and focus early on. “Cutting carbs often cuts ultra-processed snacks and sugary drinks too, so blood sugar may be steadier,” says Shyamala Vishnumohan, Ph.D., APD. With fewer rapid spikes—and the crashes that often follow—many experience fewer afternoon energy slumps. Research shows that greater glucose variability (frequent highs and lows) is associated with poorer cognition and memory. So, more stable blood sugar can lead to improved focus and more consistent energy, at least in the short term.
Why It May Not Last
While the short-term effects can feel amazing at first, restricting carbohydrates can backfire over time. “Carbs are the body’s primary fuel source, especially for the brain and during exercise, so prolonged restriction may lead to low energy, poor workout performance, mood changes and difficulty concentrating,” says Saweres.
A low-carb diet may also create nutrient gaps that can affect overall health. “Unfortunately, many people lump carbohydrates into one category, when really, some are truly nutrient powerhouses,” says Theresa Mazza, RDN, CHES, M.P.H. Fruits, vegetables, whole grains and legumes are nutrient-rich carbs packed with fiber, vitamins and minerals. When carbs are restricted, these beneficial foods are often limited as well.
Research shows that people following low-carb diets often exceed recommended intakes of saturated fat, total fat and sodium while falling short on fiber, potassium and several key vitamins. Little by little, this pattern can contribute to constipation, higher cholesterol levels and missed benefits from protective compounds found in plant foods.
“The diet can also be hard to sustain socially and psychologically, increasing the likelihood of rebound eating or weight regain,” says Saweres. When foods feel “off-limits,” the desire for them often increases, making long-term adherence harder. In many cases, this isn’t a lack of discipline, but the body and brain responding to prolonged restriction.
That’s why dietitians often recommend a more flexible approach. Instead of cutting out entire food groups, small shifts in the type, amount and pairing of carbs can support energy, satisfaction and lasting results—without the side effects of strict restriction.
What to Do Instead
Focus on Carbohydrate Quality, Not Elimination. “Rather than eliminating carbohydrates, I typically recommend focusing on carbohydrate quality and overall balance,” says Crimi. Research consistently shows that diets rich in high-fiber, plant-based carbs support heart health, gut health and long-term weight management. Opt for minimally processed, unrefined carbohydrates and choose whole grains when possible.
Pair Carbs with Protein, Fiber and Healthy Fats. Balanced meals that combine carbs with protein, fiber and healthy fats slow digestion and increase satiety (feelings of fullness.) “This approach also supports stable blood sugar, sustained energy and long-term adherence,” shares Saweres.
Aim for Consistency, Not Perfection. Being flexible helps prevent all-or-nothing thinking that can make habit change hard to stick to. “If a plan feels restrictive, people often burn out,” says Vishnumohan, which is why a balanced and less restrictive approach usually wins over extremes.
Consider Your Goals and Health History. A lower-carb pattern may help in some situations (e.g., insulin resistance or polycystic ovary syndrome), but the right amount varies widely., Working with a registered dietitian can help tailor carb intake to activity level, preferences and medical needs.
Our Expert Take
Low-carb diets can feel incredible at first—especially when they lead to quick weight loss and more energy. But as our experts explain, those short-term benefits don’t always tell the whole story. In the long run, cutting carbs can make it harder to meet your body’s energy and nutrient needs and may increase cravings, making the diet harder to stick to. Instead, nutrition experts recommend a balanced eating pattern built around minimally processed, fiber-rich carbohydrates, along with protein and healthy fats. This approach supports steadier energy, better digestion and long-term health.
