Most people believe that if your goal is fat loss, you should start with aerobic workouts and lose the body fat first before adding weight training. That is a big mistake and here's why: Obviously, weight training is the chief element in developing strength and muscle mass. What few people realize is that weight training can also increase fat loss dramatically, so by skipping the strength training in favor of aerobic-only training, you are not increasing your fat loss - you are slowing it down!"
Weight training is anaerobic and therefore burns primarily carbohydrates (sugar) during the workout. Cardiovascular exercises such as jogging, cycling, step classes, or stairclimbing are aerobic and therefore burn primarily fat during the workout. So it seems logical to focus on aerobic training for fat loss. What you're missing if you skip the weight training is the benefits that accrue after the workouts.
Something interesting happens "beneath the surface" when you lift weights. Intense, progressive weight training increases your lean body mass - aerobic training does not. Excessive aerobics combined with low calorie dieting or aerobic training without weight lifting can even cause muscle loss. If you lose lean body mass, your metabolism slows down, and this makes it easier to gain fat and harder to lose it. If you increase your lean body mass, you increase your basal metabolic rate, and fat loss becomes easier. Best of all, you increase metabolism and fat burning even when you're not working out...
Weight training provides an additional short term increase in metabolic rate after the workout, called "excess post exercise oxygen consuption" or EPOC for short. It's a myth that "all exercise" keeps you burning calories for hours after the workout. Only high intensity exercise increases post workout energy expenditure substantially and weight training has the greatest effect of all. (High intensity cardio also has a high EPOC, but thats the subect of another article). This explains why bodybuilders, who train with weights religiously and have extremely high muscle to fat ratios, can stay lean year round without doing much aerobic work.
Losing body fat as quickly and efficiently as possible requires a three-pronged approach: (1) balanced nutrition from natural foods, (2) aerobic training, and (3) weight training. All three ingredients are essential. If you neglect any one of these components, it will compromise your results because you lose the "synergy" created from this combination.
In "The Seven Habits of Highly Effective People" Author Steven Covey wrote, "Synergy means that 1 + 1 may equal 8, 16, or even 1600. Synergy is everywhere in nature. If you plant two plants close together the roots commingle and improve the quality of the soil so that both plants will grow better than if they were separated. If you put two pieces of wood together they will hold much more than the total of the weight held by each separately. The whole is greater than the sum of its parts."
When you include weights, cardio and balanced nutrition in your fat loss regimen, the effects of the three parts brought together are not linear, they are exponential. Each part complements the others and multiplies your results. You develop an efficient metabolism and a lean, muscular body that could not be achieved with one or even two of the components in isolation.
The best you can hope for from diet and aerobics alone is to become a "skinny fat person." You may lose weight from diet and aerobics, but much of it will be muscle, your fat to muscle ratio will plummet and you will take on a "soft" appearance. It's not uncommon for a woman 5 feet 4 inches tall to weigh 125 pounds and yet have 25-30% body fat. According to the Metropolitan Life height and weight tables, 125 pounds is ideal for a medium-framed 5’ 4" female, but 25-30% body fat is extremely poor for anyone! Without the weight training, you will never optimize your muscle to fat ratio and you will always struggle to keep fat off permanently.
If you have extremely limited time, and your main priority is to lose fat, then you can keep your weight training brief - maybe 30 minutes 3 days per week - and spend the rest of your time concentrating on cardio. But never neglect the weights completely - always do both, and if possible, devote an equal amount of attention to each.
Last, but not least, don't forget that weight training, not cardiovascular training, is "shapes" and sculpts your muscles. Simply put, lifting weights makes you look better! If you want a lean, hard, fat-free body, then get out of the aerobics studio, get off that bike or treadmill, and pick up some barbells and dumbbells! Lifting weights isn't just for "muscle-heads" anymore.