Why do I weigh less in the morning? (This happens every day.) Thanks!
Factors I can see:
Water loss through sweating during the night.
Somewhat different stance on the scale.
Do you go straight on the scale with no stop at the restroom?
You lose water through sweat and respiration.
You burn fat even while you’re sleeping (and of course you’re not eating or drinking anything.)
Most people additionally go to the bathroom upon waking, before weighing themselves.
Well… Sometimes your fecal matter will weigh about a pound and a half…
It’s not magic, and it’s nothing to be frightened about.
See the classic piece of literature “Everybody poops”… 
You also burn glycogen(mainly the brain, can’t run on fat) and you lose some water there, too.
How accurate do you think your measuring equipment is?
Yep. It can be surprising how much.
Yep. Water weight. Same thing happens to me. Sweat, respiration, pee.
Most of the reasons cited above seem unlikely to explain 1.5 pounds of weight loss, since if you sweated that much, your bed would be pretty uncomfortable by morning, and you’d have to burn over 5,000 calories to lose 1.5 pounds of fat, similar goes for burning glycogen (the water released doesn’t disappear unless you excrete it, even though you don’t have to burn as much to “lose” 1.5 pounds). Also, according to this page, respiration accounts for about 250 ml (a little over half a pound) of water loss during the entire day, of which about a third would occur overnight (and probably less because you are less active and not breathing as much). Although, if this is after you go to the bathroom, urination alone can explain a loss of 1.5 pounds, which would be about 2/3 of a liter of urine (you’d be really pressed to go though since the average bladder capacity is in that range), and the average stool weighs about 0.7 pounds.
What’s the margin of error on a bathroom scale? Is yours sitting on a hard surface or a carpet? While poop, pee and sweat individually won’t account for a pound and a half, together they could. Also, your cat gnawed off your left hand last night. Bad kitty!
I always weigh less in the morning too.
The carbon just floats away as CO2 in your breath, though, and most of the weight of both glycogen and fat is in the carbon that turns into Co2, not the hydrogen that turns into water.
Anyway, if you don’t think it is metabolism and excretion, what is your answer?
If the OP is seeing this consistently every day, I don’t see how inaccurate scales can be to blame.
But it is still impossible to burn the 5,000 or so calories overnight (if fat), a more reasonable figure might be 500 calories (and even if that were all glycogen, the associated water (4 times the weight of glycogen itself) does not simply get respired out, as an entire day’s worth of respiration is only around 250 ml with much less of that occurring during sleep); even fasting for a day won’t burn that many calories. As I said, it is most likely that they are weighing themselves after urinating/defecating, which can very easily account for the observed weight loss (plus a number of ounces lost from the other factors). Unless they do live somewhere where it is very hot and they don’t have/use A/C; water lost in sweat can be anywhere from around 100 ml to a 8 liters a day; the low end would occur with a comfortable room temperature (and again, you are sleeping for a third of the day, and body temperature and activity are lower, thus less sweat).
Clothing, glasses, wrist watch, jewelry, coins in your pockets, your wallet, and boogers from blowing your nose just before stepping on the scale.
Edit to add: your digital scale may be rounding the weight to the nearest 0.5 pounds. 157.8 to 156.7 explains almost an entire half pound of the discrepancy.
This was my first thought.
Especially with mechanical scales, I’d imagine that a significant enough temperature and/or humidity difference might affect the reading to that extent.
I would add that cheaper electronic scales I’ve used could be that far off after a matter of minutes after weighing for seemingly no reason.
Just a thought.
It would have to be consistently off one way at night and the other way in the morning. Random inaccuracies will not explain the facts as reported by the OP.
You don’t have to burn off 1.5 pounds of fat overnight.
You just have to turn 1.5 pounds of food and liquids that you consumed into energy to maintain your weight.
And if you eat healthy (for example salmon and broccoli) instead of unhealthy (fried chicken and ice cream) then the pound of food per calorie ratio is much more in your favor.
One meal turned into your body heat plus one trip to the restroom could easily explain this.
Right, but as mentioned above, one is respiring carbon as well as water, which your cite doesn’t take into account. Each inhale of oxygen weighs less than the exhale of C02 that follows it. To see how that can add up, look at trees.
Well of course you do. Everyone does. How could it be any other way? (Midnight feasts excepted). You’re not taking in any mass during the night in the form of food or drink, but you are losing mass through your metabolic processes.