The basics

Weather you want to get bigger, stronger, leaner, or all three, you need to start somewhere. It doesn't matter if you're 5 stone overweight, or as skinny as a rake, you have to start somewhere. 

The most rapid way you can change your body composition is by a combination of diet, weights and exercise. Lets say you're a complete beginner, what can you do to make fast changes?

• Weigh yourself once per week, ideally first thing in the morning. This is when you weight is most consistent, and weighing weekly avoids the day-to-day weight changes that can happen. 
• If you want to lose weight, reduce daily calorie intake by 500. If you want to gain weight increase daily calorie intake by 500. 
• Exercise 3 times a week. Thats enough to start with. Even a 20 min jog is better than nothing, and after a few weeks you'll really notice the difference. 
• Lift weights. It doesn't matter if you're male or female, weight lifting is very effective at burning calories and making you look good. Pick a weight that feels heavy after 8-12 reps, and do 3-4 sets of repetitions. I'll list basic exercises and movements soon.
• Stick at it. This is probably the most important point. Consistency is everything. There is a reason people with great figures turn heads - because they're uncommon, but loads of people work out - they simply don't stick at it!