Statistics are used in the 3D Universe and HD Universe games to indicate progression in certain areas, or to enumerate certain activities — for example, a "Longest wheelie" statistic will measure how long a player has sustained a wheelie on a motorcycle; "Packages collected" counts how many Hidden Packages a player has acquired; "Hospital visits" counts how many times a player has been Wasted on their current playthrough, etc.
Many of these statistics are also present in older GTA games, but they are not detailed here.
Being overweight will naturally change CJ's appearance, dialogue (mostly related to his weight) and eventually lessens most physical capabilities (including health, running speed, jumping, etc.).
Rather than recording progress or activities, these statistics are displayed onscreen during gameplay in the Heads-Up Display (HUD), to give the player a greater awareness of the protagonist's condition and situation.
GTA San Andreas has the most sophisticated miscellaneous statistics in any GTA game to this date, viewable either by holding the 'status' button or key, or via the Main Menu.
Eating too much in one sitting will cause CJ to vomit.
It's dangerous to eat somewhere between 9 to 12 of the largest or salad meal at any restaurant.
For every 150 seconds of running, or every 100 seconds of biking or swimming, CJ will shed 1.5% fat.