You lower your BMI by losing body fat slowly and sustainably, because BMI is simply your weight in kilograms divided by your height in meters squared, so any reduction in body weight produces a direct drop in the number. The CDC recommends a safe rate of 1 to 2 pounds per week, achieved through a modest calorie deficit and regular physical activity. That pace feels slow, but it is the rate at which the body preferentially loses fat rather than muscle, and it is the rate most associated with keeping the weight off long-term.
This article is general health information and is not a substitute for professional medical advice, diagnosis, or treatment. If you have a health condition, are significantly overweight, or are considering a major change to your diet or exercise routine, speak with a doctor or registered dietitian before starting.
How BMI relates to your weight
BMI stands for body mass index. The formula is weight (kg) divided by height (m) squared, or in US units, weight (lb) multiplied by 703 and then divided by height (in) squared. The result is a single number that places you in one of four standard categories: underweight (below 18.5), normal weight (18.5 to 24.9), overweight (25 to 29.9), or obese (30 and above). Because height is fixed for an adult, BMI moves only when weight moves. Lower your weight and your BMI falls by exactly the same proportion.
It is worth reading our article on whether BMI is accurate before setting a hard target. BMI does not distinguish muscle from fat, does not account for where fat is stored, and can misclassify muscular athletes as overweight. Even so, for most people who are not elite athletes, it is a useful screening number. Our article on what is a healthy BMI covers the ranges in full and puts them in context. Use the calculator below to find your current BMI and the weight you would need to reach a specific target.
Set a realistic target before you start
Research consistently shows that a 5 to 10 percent reduction in body weight produces meaningful health gains, including improvements in blood pressure, blood sugar, and cholesterol, even before a person moves into a lower BMI category. That is the most evidence-backed first target to aim for. For someone who weighs 200 pounds, 5 percent is 10 pounds and 10 percent is 20 pounds. Both are achievable within a few months at the recommended rate.
For reference, here is how percent weight loss translates to a BMI drop for an example person who is 5 ft 6 in tall and currently weighs 186 lb, giving a starting BMI of 30.
| Weight loss | Pounds lost | New weight | New BMI |
|---|---|---|---|
| 5 percent | 9 lb | 177 lb | 28.6 |
| 10 percent | 19 lb | 167 lb | 27.0 |
| 15 percent | 28 lb | 158 lb | 25.5 |
Even the 5 percent loss at this example moves the person out of the obese range and into the overweight range. The 15 percent loss brings them to the edge of the normal range. Neither requires extreme measures. Both are achievable over four to six months at a steady 1 to 2 pounds per week.
Step 1: Create a modest calorie deficit
A calorie deficit is the foundation of fat loss. One pound of fat stores roughly 3,500 calories, so a daily deficit of 500 calories produces about one pound of loss per week, and a 750-calorie deficit produces about 1.5 pounds. Both fall within the CDC-recommended safe range. You do not need to count every calorie obsessively, but having a rough idea of your maintenance intake and cutting it modestly is the most reliable starting point.
Avoid cutting more than 1,000 calories a day below maintenance. Larger deficits accelerate muscle loss, slow the metabolism, cause fatigue and hunger that leads to rebound eating, and make the diet unsustainable. A smaller, consistent deficit outperforms a large, short-lived one almost every time.
Step 2: Eat more protein
Protein is the single most important dietary lever for fat loss. It increases satiety, which means you feel full on fewer calories. It has a higher thermic effect than carbohydrates or fat, meaning the body burns more calories digesting it. And it preserves lean muscle mass during a calorie deficit, which keeps your resting metabolism from falling as sharply as it otherwise would. Lean sources include chicken breast, fish, eggs, Greek yogurt, cottage cheese, legumes, and tofu.
A practical target for most people in a weight-loss phase is 0.7 to 1 gram of protein per pound of body weight per day, or about 130 to 185 grams for a 185-pound person. You do not need supplements to reach this; most people can hit it through whole food sources if they build each meal around a protein anchor.
Step 3: Prioritize fiber and whole foods
Fiber slows digestion, blunts blood-sugar spikes after meals, and contributes to lasting fullness. Vegetables, fruit, legumes, and whole grains are all high in fiber and also tend to be lower in calories relative to their volume than processed alternatives. Replacing refined grains with whole grains, and reaching for whole fruit instead of juice, are two changes that most people notice are filling rather than restrictive.
Ultra-processed foods are engineered to override satiety signals. They are not forbidden in a sustainable diet, but reducing their share of total intake is consistently associated with lower calorie consumption, even without counting. The simplest version of this principle: build meals around vegetables, lean protein, and whole grains, and treat highly processed items as occasional rather than staple foods.
Step 4: Combine cardio with resistance training
The American College of Sports Medicine recommends 150 to 250 minutes per week of moderate-intensity activity for weight maintenance, and 250 or more minutes per week for meaningful weight loss. Moderate intensity means activity at which you can speak in short sentences but not sing, such as brisk walking, cycling, or swimming.
Cardio burns calories and improves cardiovascular health, but adding resistance training two to three times a week is what preserves muscle during a deficit. When you lose weight without strength training, a meaningful portion of the loss comes from muscle rather than fat. This lowers your resting metabolic rate and makes the weight easier to regain. Resistance training keeps muscle on, so the weight you lose is predominantly fat, your metabolism stays higher, and your body composition improves even when the scale moves the same amount.
Step 5: Hit a daily step goal
Non-exercise activity, the walking and movement woven into daily life, contributes significantly to total daily calorie burn. A step target of 8,000 to 10,000 steps a day is associated with lower BMI and better metabolic health across multiple population studies. For many people, reaching that number requires deliberate effort: parking farther away, taking stairs, walking during phone calls, or breaking up long sitting periods with short walks.
Steps are not a substitute for structured exercise, but they provide a large and consistent calorie burn that accumulates over weeks and months in ways that are hard to offset. A person who adds 3,000 steps a day burns roughly an extra 100 to 150 calories daily, which is 700 to 1,000 extra calories a week without any formal workout.
Step 6: Prioritize sleep
Sleep is the most underrated fat-loss lever. One controlled study found that participants who slept 8.5 hours per night during a calorie deficit lost about 55 percent more fat than those who slept 5.5 hours per night on the same calorie intake. Poor sleep elevates ghrelin, the hunger hormone, and suppresses leptin, the satiety hormone, producing measurable increases in appetite and a specific drive toward calorie-dense foods the following day.
Seven to nine hours of sleep per night for most adults is not a luxury. It is a physiological requirement for effective fat loss and for the hormonal environment that makes a calorie deficit manageable rather than miserable. If your schedule makes adequate sleep genuinely difficult, that constraint is worth addressing before or alongside a diet and exercise plan.
Step 7: Track your progress consistently
Weight fluctuates 2 to 4 pounds day to day from water, sodium, food mass, and hormonal shifts. A single morning weigh-in tells you very little. What matters is the trend over two to four weeks. Weigh yourself at the same time each morning, after using the bathroom and before eating, and look at the weekly average rather than any individual reading.
Also track waist circumference, which reflects visceral fat more directly than the scale, and pay attention to how clothes fit and how your energy and strength feel. A plateau on the scale that coincides with a shrinking waist is progress. The BMI calculator above can help you check your number as you hit weight milestones along the way.
Avoid crash diets and very low-calorie approaches
Crash diets, typically defined as eating below 800 calories a day, do produce rapid initial weight loss, but the majority of that early loss is water and glycogen, not fat. When calorie intake drops that sharply, the body reduces lean mass at an accelerated rate, slows thyroid output, and lowers the resting metabolic rate to compensate. The result is that when normal eating resumes, weight returns quickly, often above the starting point, because the metabolism is now running lower than it was before the diet began.
Studies on very low calorie diets consistently show that most participants regain the weight within one to five years. The goal is not to find the fastest way to a lower BMI number on a single date. It is to build a body and a set of habits that maintain a healthy weight for decades. The 1 to 2 pounds per week approach wins on both counts: it produces meaningful fat loss and it is a pace most people can sustain long enough for the habits to stick.
When to see a doctor
Most healthy adults can begin a moderate diet and exercise program without a medical consultation. However, speak with a doctor before starting if any of the following apply to you:
- You have a BMI above 35, or a BMI above 30 with a weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnea.
- You have not exercised regularly in several years and plan to begin vigorous activity.
- You have a history of heart disease, kidney disease, or any condition that affects how your body handles dietary changes.
- You are pregnant or breastfeeding.
- You have a personal or family history of an eating disorder.
A doctor can run bloodwork to identify underlying contributors to weight gain, such as hypothyroidism or insulin resistance, that a diet alone will not fix. A registered dietitian can build a calorie and protein plan tailored to your actual maintenance needs, which produces better results than generic online calculators. For substantial weight loss, professional guidance is not a luxury.