What impact does air have on our weight? Although air is light, it is fluid. So it must exert upthrust on people. So does it mean, in fact, we are heavier than our weight? Also, the gravitational acceleration is bigger than its value?
 A: Yes we would be heavier (weigh more on a scale) if we were in a vacuum than atmospheric air, but it would be very little because the density of air (about 1.29 kg/m$^3$) is much less than that of the human, which is approximately that of water (1000 kg/m$^3$).
For air density of 1.29 kg/m$^3$, a 75 kg human body of volume 0.075 m$^3$, the buoyant force is
$F=\rho g V$= (1.29 kg/m$^3$)(9.8 m/s$^2$)(0.075 m$^3$)= 0.95 N=1 N
Making the weight of the person 1 N (= 0.1 kg), or 0.13 percent, more than the scale reading of the person.
Hope this helps.
A: A human at sea level on Earth will experience a buoyant force equal to the volume of their body times the density of air, pointing upward against gravity. This works out to about 75 grams for an average human weighing about 62 kilograms- a small amount.
Also please note that as a recovering ex-engineer, I interchange mass and force units with easy unconcern- as I consider such trifles to be mere trifles.
A: If this is related to atmospheric pressure then:-
The buoyancy force due to the air density surrounding objects does affect the weight measured by a weighing scale, but the effect is quite small. The density of air is at standard sea level conditions is 1.225  kg/m3 . Plastic objects have a density near that of water, which is 1000  kg/m3 . Metals are a few times denser than water. So the effect of the buoyancy force due to air is about 1 part in a thousand, or about 0.1%. If you need to weigh something more accurately than that, then you would have to correct for this. For most practical purposes, it’s too small to worry about.
People sometime calibrate a weighing scale by weighing standard weights, which are made of metals, such as brass or steel. The buoyancy force is sort of included in that, so at least for metal objects, the error would be even smaller than 0.1%.
When you need to make very accurate measurements, you would need to account for buoyancy from the air, but you’d also need to correct for effects due to temperature on the weighing scale.
Later: Air density if affected by air pressure as well as temperature and humidity, so atmospheric pressure (which you asked about) affects weight measurements, but not directly. It’s through the effect pressure has on density of air.
In terms of air pollution , there is some new research going on whether air pollution could cause obesity .
A: Yes, We would be heavier in vaccum than our atmosphere.
I don't understand how are you measuring that acceleration.
If you are doing it by calculating g from equation $Gm_1×m_2/m^2 r^2 $
then,
Gravitaional value is not bigger. In normal by saying weight we mean force. The mass is same all the time.  That's why gravitational acceleration will remain same while the actual acceleration due to factor like atmosphere will change.
