Atkins diet is bleeding stupid............ no carbohydrates? can be dangerous, particularly if you have an undiagnosed condition underlying. Then eating nothing but protein........... looking at a variety of problems, including kidney damage.
Just eat less calories than you burn up, then you'l lose weight, avoid any food that has fat greater than 5% (except for the odd burger anyway) and exercise a bit more.
Average calories in a day for a grown man is 2500 to 3000 required for normal activity, more if you are active.
Carbohydrates have half the calories of fat (by weight) and are processed quicker, so day of a tourney... eat pasta, rice, fruit etc (or sandwiches..no butter/marge)... by the end of the day, you'll have burned off the calories you've taken in and started on your fat reserves........ cut back on fat etc..... over the next week, then see if you've lost anything.
Also beer...... 200 calories a pint, so if you drink ten pints in a week: that's a whole extra days calories!!!!!!!!
Spirits are nearly as bad..... alcohol is pure energy, almost as good as sugar for weight gain.
And before anyone posts to correct the little details (you know who you are) I know I'm being a bit general, but the majority of people don't want a full on science lesson.