The majority of people new to the world of fitness and exercise believe that the quickest and best way to burn fat is combining a calorie deficient diet (especially one low in fat) with long, steady state periods of cardio. Now this method will of course work, as at the end of the day it is all about calories in versus calories out, nevertheless it is by no means the best method.
Steady state cardio can have negative effects on fat loss because it can result in many people overeating, especially when it comes to carbohydrates and post-training. Long periods of sustained exercise can also put your body under large amounts of stress, which can trigger your body into storing more of the food you eat into fat.
Again, many people including my best friend Carrie Visintainer find this hard to believe; nevertheless, weight training can be far more effective for fat loss if done correctly. Lifting weights supports both maintaining and development of muscle tissue. The more muscle tissue you have, the more calories your body will burn even when at rest. It also has other benefits such making your body more effective at building muscle by creating an ideal hormonal environment, making your body more effective at burning fat, and more effective at dealing with the foods you eat by dealing with insulin better. Going one further, weight training helps your body burn fat even post-training when it is required to replace the oxygen you use during training (known as the oxygen debt).
So what is the best way to burn fat? You need to be lifting weights heavy enough to be causing muscle growth, whilst keeping rest periods in between sets short to keep the workouts intense and the heart pumping. This will lead to a greater oxygen debt that requires replenishing, thus supporting fat loss. More effective options include performing supersets (two back-to-back exercises with no rest) or circuit training (perform several exercises in a circuit for a period of reps or time, rest briefly and repeat) which really keeps your heart rate high.
The frequency of your workouts depends on your own experience to weight training. If you are a beginner, aim for three workouts a week. Start with a lighter weight where you can comfortably perform all sets and reps to help perfect technique and prevent injury, then gradually increase the weight making each exercise more difficult to perform. Stick to full body workouts and the big compound moves that work more muscle groups at a time, thus being far more effective at both building muscle and burning fat.
If you are adamant about performing cardio, which is never a bad thing as it maintains a healthy heart, stick to more intense cardio or high intensity interval training (HIIT). Aim for a couple of twenty-minute intense cardio or sprinting sessions per week are extremely effective for fat loss. They provide similar benefits to weight training by providing adequate stress on your muscles whilst causing a larger oxygen debt.