Combining a diet and exercise program, you can lose about 25 pounds in three months in a healthy, safe manner, according to organizations including the Centers for Disease Control and Prevention. You don’t have to feel constantly hungry or kill yourself on an exercise machine every day if you map out a sensible plan in advance.

Calculate your recommended daily calorie goal for weight maintenance as the first step in creating a weight-loss plan. Meet with a health professional, use an online calorie calculator or visit the U.S. Department of Agriculture’s website. Subtract 500 calories from that number to get your daily calorie deficit goal for losing 1 pound per week, or 1,000 calories from that number to lose 2 pounds per week. Regardless of your weight maintenance number, you should always eat at least 1,200 calories per day.

Create a plan for combining diet and exercise to meet your three-month weight-loss goal. Subtract 250 calories from your recommended daily calorie number each day and perform enough exercise to burn 250 calories each day if you want to lose 1 pound per week. Use different combinations of those numbers if you want to emphasize diet or exercise, lose more than 1 pound per week or eat more calories on days when you don’t exercise.

Plan each day’s meals and snacks in advance using nutrition labels to guide you. Eat breakfast each day to prevent long gaps between meals, which can lead to extra fat storage and overeating, Mayo Clinic nutritionist Katherine Zeratsky recommends. Include healthy midmorning and afternoon snacks to regulate your blood sugar levels and decrease hunger pangs that cause you to overeat at meals.

Perform exercise with some resistance at the maximum heart rate you can sustain without stopping until you meet your daily calorie-burning goal. Walk at a brisk pace if that is the most intensity you can use during your first two or three weeks. Perform full-body workouts, such as adding dumbbells to walks or exercise bike workouts or using a rowing machine. Use a heart rate monitor with a calorie counter function or use an online exercise calorie counter to determine how long and how hard you should exercise to burn your target calories each day. Increase your workout intensity or duration or both each week as you build strength and stamina.

Keep a diet and exercise journal. Record your calories eaten and calories burned each day. Make notes on which foods you enjoyed eating and which meals and snacks didn’t hit the spot. Note which exercises, machines, weights and workouts challenged you and which didn’t leave you feeling as though you had worked your hardest, and modify your workouts to keep you close to your limit of exhaustion.

Change your exercise routine each week to prevent a weight-loss plateau. Use different machines and perform varied activities, such as walking, swimming, using a cardio machine, lifting weights, jumping rope, performing calisthenics and running stairs. Focus on using your muscles differently. For example, switching from an elliptical to a stationary bike uses lower-body muscles in a similar fashion. Instead, change from an elliptical to a rowing machine or using a home gym.

Monitor your weight regularly to motivate yourself and determine if you need to cut more calories or exercise longer. Women who regularly weighed themselves lost more weight than those who didn’t, according to a study published in "Nutrition Journal" in 2009.

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