what can i do to increase my metabolism?

Have you tried HIIT? (High intensity interval training)

It raises your metabolism long after you're done working out and burn more fat in LESS time than steady state cardio.

I can give you an example:

Warm-up (could be walking or jogging 5 minutes)

Sprint 30 seconds

Walk 30-90 seconds (what feels best for you)

Sprint 30 seconds

Walk 30-90 seconds

Do these sprint intervals 4-6 times to start with and increase every couple of weeks.

You'll turn into a fat burning machine. You can also search google for much more information, just type HIIT.

The more muscle you have, the faster your metabolism. There are products (natural and not) that claim to boost metabolism, but I've never heard of any that made a significant difference.

If you like green tea, it's supposed to help and is beneficial in other ways also...so certainly couldn't hurt.

Eating smaller than normal healthy meals every two to three hours will help speed up your metabolism. It helps prevent your body going into starvation mode, which your body automatically starts to store food that you eat into fat to reserve it for later. If you consistently eat every two or three hours your body will get used to the feedings and will start to burn the food for energy instead of storing it into fat.

Think of a fire. If the wood that you put on the fire will burn rather quickly, but once you don't put wood on to keep it blazing it will typically slow down and die out. If you continue to put wood on the fire it will continue to blaze putting out maximum heat/energy. The key is that it really does need to be good lumber (healthy foods - chicken, tuna, most fish, lean turkey, low-fat cottage cheese, 100% whole wheat bread, brown rice, sweet potatoes, etc.).

The other nice thing is that since you are constantly eating, you are less likely to be tempted to eat easy access junk food since your belly will typically feel full.

Drink really really cold water. RESPECT!!!