How does alcohol absorption differ in heavy vs light individuals?

How does body weight affect how quickly alcohol enters the bloodstream?
Alcohol spreads through body water. Heavier people have more total body water, so the same drink produces a lower blood-alcohol concentration than it does in lighter people. The liver still processes alcohol at roughly one standard drink per hour regardless of size, but the peak level reached is lower in heavier drinkers.

What changes if the heavier person also has more muscle versus more fat?
Muscle holds more water than fat. Two people of the same weight can reach different blood-alcohol peaks if one has a higher muscle-to-fat ratio. The leaner individual dilutes the alcohol across a larger water compartment and therefore shows a lower reading on a breath or blood test.

Does drinking on an empty stomach erase the body-size difference?
Food slows stomach emptying, so absorption takes longer in anyone who has eaten. The size-related difference in peak concentration remains, but the time to reach that peak stretches for both heavy and light drinkers when they eat beforehand.

How do health guidelines adjust drink limits for different body sizes?
Most public-health advice sets one standard drink as 14 g of alcohol and recommends no more than one drink per hour for safety. Because lighter people reach higher blood-alcohol levels from that same drink, some countries publish lower daily limits or explicit per-kilogram guidance for smaller adults.

When do breath or blood tests become unreliable across body weights?
Standard breath analyzers estimate blood alcohol from a fixed ratio. In very heavy or very lean individuals the actual water distribution can differ enough from the assumed average to produce modest errors. Police and medical labs sometimes switch to direct blood measurement when body-composition extremes are suspected.

[1] https://drugpatentwatch.com/