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I've heard this multiple times as an explanation to eating more in relation to being exposed to colder temperatures (restaurants that are colder, during the winter, etc.) but I have yet to be able to find any concrete scientific evidence to prove it.

Most of what I have found is based on theory, such as:

Heat-Production theory suggested by Brobeck (as cited in Franken's, 1994 textbook Human Motivation) states that we feel hungry when our body temperature drops, and when it rises, the hunger decreases. [1]

While this explanation makes sense, is there any hard evidence in claiming that temperature alone can increase hunger?

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    Restaurants seem to be kept cold? I've never heard or experienced that, unless you're talking about public places in US summers in general, with extreme airconditioning. For the rest I've experienced rather the opposite, with restaurants switching on terrace heating for outside when it's not cold at all, making me move to another restaurant. Can you clarify the "cold restaurants" claim part? – gerrit Nov 30 '17 at 21:29
  • Well, I used reference to the restaurant claim because that's where I originally heard it but the focus of this claim is just that being cold makes you hungry. Should I edit to clarify? – Jess K. Nov 30 '17 at 21:32
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    I have heard the claim before, but I would clarify to make sure people don't confuse it with the very different claim that restaurants by conspiracy keep their places cold to encourage people to eat more. – gerrit Nov 30 '17 at 21:35
  • Cold weather MREs contain more calories "The caloric and fat content of the meals is also increased". That doesn't really prove much but it might be easier to answer if cold weather increases food consumption instead of someones feelings. – daniel Nov 30 '17 at 22:54
  • I think most people will agree that being too warm tends to suppress your appetite, or at least your tendency to overstuff yourself. The other way is less obvious. – Daniel R Hicks Dec 1 '17 at 0:58
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There's alas not much in the way of data on this. One experimental study published last year said (buried in the body of their paper) that subjective feeling of hunger increased during 1.5 hours of mild cold exposure (18C vs 24C), but that there wasn't a significant difference in actual food intake in this experiment (and the latter was their main conclusion).

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During cold exposure, feelings of hunger showed a trend to increase to a level above what was observed during thermoneutrality. Feelings of hunger increased during both situations over 150 min. A trend towards a higher hunger score during cold was observed (Fig. 6A, repeated measurement ANOVA for the effect of time P = 0.021, for the effect of temperature P = 0.064). [...] During the meal, the same amount of food was consumed after thermoneutrality and mild cold exposure (2740 ± 567 vs 2878 ± 492 kJ paired t-test P = 0.69) (Fig. 6C)

The confidence level for the effect of temperature on subjective hunger observed (P = 0.064) makes the effect questionable, of course. The authors didn't even mention it in their abstract, which only said that

It is concluded that short-term mild cold exposure increases energy expenditure without changes in food intake.

But they do say this in the discussion:

Whether prolonged mild cold exposure, with meals consumed in the cold, would increase energy intake remains to be determined. Historical data obtained under harsher thermal conditions show a negative correlation between outdoor temperature (ranging from −30 to +35°C) and food intake (9). To our knowledge, there are no data on the effect of prolonged mild cold exposure on hunger and food intake.

  1. Blaxter K. Energy metabolism in animals and man, p 204–206. Cambridge, UK: Cambridge University Press, 1989.

I read this as there is some correlation but causation is not proven, possibly because the effect size is small so a large dose and/or a longer exposure time may be needed to have enough power in the experiment.

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If you are cold, your body will be trying to produce energy to generate heat. Calories are a measurement of energy. We consume food (calories), the body turns it into energy or stores for later use as fat. In order to generate the heat the body needs when it is cold, it needs to either burn this energy or use fat stores.

This is a natural process that our ancestors and many animals need in order to survive the winter time. Before the cold months when farming and hunting is virtually stopped, our bodies learned to stock up when it starts getting cold. This will help to create more insulation (fat) and provide better survivability rates so that our bodies can afford to shed 10-20 lbs due to a lack of abundant food. NPR posted an article in 2011 discussing this topic with a quick quote:

"We are driven by things implanted in our brain a long, long time ago," says Ira Ockene, a cardiologist at the University of Massachusetts Medical School who has long been interested in how seasonal variations influence our health.

When we are warm, our bodies do not want to intake any energy(food) or generate energy as the hot weather(heat) is already causing our bodies to overload. We dissipate energy from our bodies via heat to help cool down the body along with the sweat that the body uses to naturally cool and regulate our temperature. Intaking more energy (food) would cause our body temperatures to rise slightly.

How Eating Affects Body Temperature

Eating generally leads to a slight increase in body temperature, as your metabolic rate increases in order to allow the digestion of food. Your temperature may increase by as many as 2 degrees F as the chemical reactions of the digestive process take place within your body. These chemical reactions are what produces the heat that causes a slight augmentation in body temperature.

This is a big reason why many diet pills often claim to reduce hunger and burn fat via a thermic reaction.

So in conclusion, much of this has to do with our seasonal reactions that have been embedded since before the modern comforts and luxuries. There is evidence that temperatures do directly affect our hunger via how we regulate heat/energy and as a learned survival instinct.

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    This just restates the theory mentioned in the question at greater length. Is there empirical evidence supporting this? If we divide a mass of people into groups and put them in rooms with different temperatures and track their consumption, do the people in the colder rooms consume more? Bonus: Does it matter whether the food is free or purchased by the item? – Brythan Nov 30 '17 at 22:12
  • @Brythan there seems to be no empirical hard facts of this but here is another study on the topic that can surmise the same conclusion. You also have to remember you stated it correctly with the term theory. That implies that there is not enough data to yet claim it as a scientific law but enough to at least have it as a theory. This is just another scientific theory that is waiting to become a scientific law. – ggiaquin16 Nov 30 '17 at 22:21
  • @Brythan I also didn't merely restate the OP's theory. I explained the process of energy and the conversion of food to energy as it relates to temperature and how external temperatures can play a factor (whether significantly or not). Provided were examples of how animals and our bodies naturally prepare for cold winters at an instinctual level as well as provided examples of food nutrition that have been proven to aid in the processing of energy. Yes there is no hard facts, empirical data, or black and white studies, but there is plenty of surmised data to still validate the claim. – ggiaquin16 Nov 30 '17 at 22:31
  • @Brythan to answer your hypothetical test, I would be fairly interested in that and I can only speak to how my body would react and suspect that others would generally follow. If the food was free, there would be little competition, everyone would be able to eat at will. If the food was not free, it would eventually cause competition as those who do not manage food budget will run out and be forced into drastic measures to survive. From the temperature standpoint, I know with myself as stated earlier, (continued) – ggiaquin16 Nov 30 '17 at 22:35
  • I would generally be less hungry when it is hot, and more hungry when the temperatures normalize than when it is hot, and even more so when it is colder. Having experienced life in a desert (Arizona/Saudi Arabia), and colder regions where there is snowfall and close to 0 temperatures (New York/New Jersey area) that is at least how my body reacted. – ggiaquin16 Nov 30 '17 at 22:39

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