Increasing the amount of activity you get throughout the day is often recommended for people trying to slim down, but exercise alone isn't always enough to bring about a significant amount of weight loss. How often you should work out for this purpose depends on your intensity level and the length of each session, as well as the amount you eat each day. Check with your doctor before starting a new exercise program to ensure it is safe for you.
Recommended Cardio for Weight Loss
For weight-loss purposes, it's best to get at least 300 minutes per week of moderate-intensity cardio, which means you're exercising hard enough to be able to talk, but not sing. If you're short on time, you can increase the intensity and do 150 minutes per week of vigorous cardio, enough that you're working hard enough so that you can no longer hold a conversation. Spread your workouts throughout the day and week, as long as each session lasts at least 10 minutes.
Intensity vs. Time
Both the length and intensity of exercise play a role in weight loss, especially if you're relying on exercise alone to get thinner. Those who exercised longer at a vigorous intensity -- the equivalent of jogging 20 miles each week -- lost more weight and body fat than those who either exercised less time or at a moderate or vigorous intensity, according to a study published in Archives of Internal Medicine in 2004.
Cardio Calorie Considerations
Not everyone manages to lose weight with exercise alone, for a number of reasons. First, people often overestimate the number of calories they burn through exercise by three or four times, according to a study published in the Journal of Sports Medicine and Physical Fitness in 2010. You need to burn an extra 3,500 calories to lose 1 pound through exercise. A person who weighs 160 pounds burns about 200 calories walking for an hour at 2 miles per hour, which means it would take about 17 hours to lose 1 pound doing this activity. This same person would burn about 315 calories downhill skiing or golfing while carrying clubs for an hour, and about 365 calories using an elliptical machine or doing low-impact aerobics for the same amount of time.
Potential Compensatory Behaviors
Although it's possible that you may not be losing weight because you're building muscle, this isn't the most likely reason for a lack of weight loss due to exercise. People often compensate for any calories they've burned during their workouts by either being less active the rest of the day or eating more, noted a review article published in Medicine and Science in Sports and Exercise in 2014.
If you find that you're not losing weight within a few weeks, you may want to start making some dietary changes. A study published in the Journal of Strength and Conditioning Research in 2015 noted that if you don't experience changes in your weight after four weeks of exercising, you aren't likely to lose weight by exercise alone.
Benefits of Adding Strength Training
Although strength training doesn't usually burn as many calories as cardio, you shouldn't leave it out of your exercise regimen if you're trying to lose weight. In those who don't do at least the recommended two strength-training sessions per week, about 1 out of every 4 pounds lost comes from muscle instead of fat. This loss of muscle can slow down your metabolism and make it harder to lose weight. The combination of strength training and a high-protein, reduced-calorie diet can help you improve both your body composition and your weight loss results, as well as decreasing your risk for heart disease and type 2 diabetes, noted a study published in Diabetes Care in 2010.
Dieting tends to be more effective for weight loss than exercise, but exercise may be more important for keeping off any weight you lose. For the best results, you should do both. People who followed a reduced-calorie diet and exercised lost more weight and achieved greater improvements in body composition than those who either dieted or exercised alone, according to a study published in 2012 in Obesity.
Making dietary changes can increase the weight-loss results you achieve through adding exercise to your daily routine. Cutting 500 calories from your diet each day can help you create the necessary 3,500 calorie deficit to lose weight at a rate of about 1 pound per week. Do this by cutting out highly processed foods, refined grains and sugary or fatty foods, and concentrating on fruits, vegetables, whole grains and lean protein foods.
Protein is particularly important when you're attempting to lose weight. Eating a higher protein diet helps increase the beneficial effects of exercising on your body composition, according to a study published in 2005 in The Journal of Nutrition. You need protein to build muscle, and muscle helps increase your metabolism.