I experimented for a time on almost zero carbs. I ate about 3000-3500 calories a day, 1500-2000 of it straight fat, while maintaining somewhat defined abs, despite plenty of gym time. The key here is INSULIN. It is why SADers gain weight so easily. Here's the gist:
When you consume any carbs, it all ends up as glucose in the blood stream (blood sugar). Your pancreas then produces insulin to regulate this blood sugar to make sure it doesn't get too high. Insulin tells you cells to become recpetive to taking in food/nutrients, and to convert any glucose not used immediately for energy to fat.
So... if you are eating tons of fatty meat with no carbs, your body will be more inclined to let much of it pass through and not absorb, no matter how much you eat, because you have not triggered the horomone to make your cells absorb. The solution to this is rather simple: eat some non-starchy, non-sweet fruit with your meat. I will often put 1/2 a bell pepper, 2 jalapenos, 1/2-1 tomato, 1 mushroom in a food processor to make salsa. I'll mix this with 1 pound of ground beef and eat for lunch, and repeat for dinner. Also, berries and eggs are a great pre/post work-out combination or breakfast.
Here's a great way to get what your looking for at low demand: When you get up in the morning, do push-ups. Install a pull up bar, and throughout the day, stop and do pull ups (maybe in the bathroom - every time you pee, you knock out 5-15 pull-ups). In a month, start chaning it up. Spread your arms wide, bring them in close, do over hand, do underand, do combos of all the above. Prop your feet up and do incline push ups, hell, get against a wall and do hand-stand push ups. This should be plenty for you to put on 5-10 pounds over the course of a few months.
