Unwanted weight loss usually comes down to one of two problems: you’re not eating enough calories to match what your body burns, or a medical issue is preventing your body from absorbing or holding onto the energy you take in. Fixing it requires figuring out which side of that equation is off, then making targeted changes to your diet, activity, and eating habits. If you’ve lost more than 10 pounds (4.5 kilograms) or 5% of your normal body weight over 6 to 12 months without intentionally trying, that crosses a clinical threshold worth investigating with a doctor.
Rule Out Medical Causes First
Several conditions can drive weight loss even when you feel like you’re eating normally. An overactive thyroid speeds up your metabolism so your body burns through calories faster than you can replace them. Digestive conditions like celiac disease, inflammatory bowel disease, and peptic ulcers interfere with how well your gut absorbs nutrients from food, meaning calories pass through you without being used. Diabetes, particularly when poorly controlled, can cause the body to break down fat and muscle for energy despite adequate food intake.
More serious conditions like heart failure, chronic kidney disease, COPD, and certain cancers can also cause progressive weight loss, especially in later stages. If your weight is dropping and you can’t explain it through changes in diet or exercise, blood work and a basic physical exam can screen for most of these. A BMI below 18.5 is classified as underweight, and below 17.0 indicates moderate to severe thinness. A BMI under 16.0 carries a markedly increased risk of serious health consequences, poor physical performance, and dangerous fatigue.
Eat More Calories Than You Burn
This sounds obvious, but most people who are losing weight unintentionally underestimate how many calories they actually need. Gaining a pound of lean muscle requires roughly 2,000 to 2,500 extra calories per week above what your body uses for daily maintenance. That works out to about 300 to 350 extra calories per day. If you’re currently losing weight, you may need even more than that just to stabilize before you start gaining.
Tracking your intake for a few days with a food diary or app gives you a realistic baseline. Many people discover they’re eating 300 to 500 fewer calories than they assumed, especially on busy days when meals get skipped. From there, the goal is to consistently add calorie-dense foods: nuts, nut butters, olive oil, avocado, cheese, whole milk, dried fruit, and granola all pack significant energy into small portions. Adding a tablespoon of olive oil to a meal adds about 120 calories without changing the volume of food on your plate.
Use Liquid Calories Strategically
One of the most effective tricks for increasing total intake is drinking some of your calories. Your body registers liquid calories very differently than solid food. Research on satiety shows that liquids trigger much weaker fullness signals than solids do. When people consumed the same number of calories as a drink versus a solid snack, they didn’t reduce what they ate for the rest of the day after drinking the liquid version, but they did eat less after the solid version. In one study, people consumed about 30% more of a chocolate-flavored liquid compared to a similarly flavored semi-solid food.
This low satiety effect, which normally contributes to overconsumption and weight gain, works in your favor when you’re trying to stop losing weight. Smoothies made with whole milk, banana, protein powder, nut butter, and oats can easily reach 500 to 700 calories per glass. Drinking one between meals adds substantial calories without killing your appetite for the next meal. Soups are a slight exception here: they’re consumed more slowly (under 100 grams per minute compared to over 200 grams per minute for most liquids), so they tend to be more filling. Calorie-dense smoothies and shakes are your better bet.
Increase Meal Frequency
If three large meals feel overwhelming, eating smaller amounts every two to three hours is a well-established strategy for increasing total daily intake. This “grazing” approach works because it sidesteps the barrier of appetite. You don’t need to feel hungry to eat a handful of trail mix, a cheese stick, or a glass of chocolate milk. You just need a schedule.
Setting alarms or pairing eating with existing habits (a snack every time you take a break, a smoothie right after brushing your teeth in the morning) helps build consistency. The goal is five to six eating occasions per day rather than three. Each one doesn’t need to be a full meal. Even 200 to 300 calories per snack adds 400 to 900 calories to your daily total, which is often enough to shift the balance from losing to maintaining or gaining.
Prioritize Protein to Protect Muscle
When you lose weight, your body doesn’t only burn fat. It also breaks down muscle, which lowers your metabolism and makes it harder to regain weight later. Protein is the nutrient that counteracts this. The minimum recommended intake is 0.8 grams of protein per kilogram of body weight per day (about 0.36 grams per pound), but that’s the floor for basic health, not the amount needed to build or preserve muscle during weight changes. Most sports nutrition guidelines suggest higher intakes for people trying to gain or maintain lean mass.
For a 150-pound person, 0.8 grams per kilogram comes out to about 55 grams of protein daily. Getting more than that, closer to 1.0 to 1.2 grams per kilogram, gives your body a better supply of the building blocks it needs to maintain muscle tissue. Practical sources include eggs, Greek yogurt, chicken, fish, cottage cheese, beans, and protein powder added to smoothies or oatmeal. Spreading protein across all meals and snacks rather than loading it into one meal improves how efficiently your body uses it.
Add Strength Training
Resistance training signals your body to build muscle rather than store excess calories as fat. It also stimulates appetite in many people, which helps with the eating side of the equation. Research on training frequency shows that the total amount of work you do per week matters more than how many days you split it across. People who trained two days per week gained the same amount of muscle and strength as those who trained four days per week, as long as the total weekly volume was identical.
This is good news if you’re already struggling with energy or motivation. Two to three sessions per week focusing on compound movements (squats, deadlifts, rows, presses, and pull-ups or lat pulldowns) is enough to drive meaningful muscle growth. Start with weights that feel challenging by the last few repetitions of each set, and gradually increase the load over weeks. The muscle you build raises your resting metabolic rate slightly, but more importantly, it ensures that the weight you regain is functional tissue rather than just body fat.
Adjust Your Environment and Habits
Small changes to how and when you eat can add up significantly. Eating from larger plates and bowls tends to increase portion sizes without conscious effort. Keeping calorie-dense snacks visible and within arm’s reach (a jar of nuts on your desk, cheese in the front of the fridge) removes the friction between you and extra calories. Eating while watching something or socializing also tends to increase intake because you’re less focused on fullness cues.
If stress, anxiety, or depression is suppressing your appetite, addressing that directly will often do more for your weight than any dietary change. Chronic stress raises cortisol, which can suppress hunger in some people and accelerate muscle breakdown. Even moderate improvements in sleep, physical activity, and stress management can restore appetite to more normal levels. If medications you’re taking list appetite suppression or weight loss as side effects (certain antidepressants, stimulants, and other common prescriptions), that’s worth discussing with whoever prescribed them, since alternatives with fewer metabolic effects often exist.