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  • Writer's pictureRenee Little, R.D.

Summer Appetite Change: When is it's ok and when do you need to act?

It's summer here in Calgary, AB and we've had a blazing hot start to the season. Initially a heat wave hit all of Alberta sending temps in the 30's and 40's which is very unusual for our area.

I personally felt my appetite decline and I also heard many others share the same experience. It got me thinking...why does this happen and is it ok for everyone? My concern was that if some folks are already having a difficult time eating enough food would the heat wave make that even more difficult and what can be done to counteract this shift in appetite?

The Physiology of a Heat Wave on Appetite

During a drastic outdoor heat increase, our bodies start to prioritize cooling to keep us alive. Thank you BODY! However this means that our bodies are putting cooling over other primary survival needs, including eating.

Our body constantly balances different demands. When there is a steep increase of temperature outside, our bodies are not yet adapted to these higher temperatures. As a result, our bodies does what it can to prioritize cooling until our adaptive mechanisms kick in and it gets acclimatized to the heat.

Why Does it Affect Appetite?

Did you know that eating food causes an increase in temperature in the body? This is known as the thermogenic effect of food. When our bodies are already too hot from external temps and not yet adapted, it reduces appetite to decrease food intake so that our internal temperature doesn’t rise further. It is a survival method.

Adaptation to Heat: Is it Ok?

When heat increases such as a heat wave are temporary we only need to survive the week or two of higher heat and then temperatures will get back to the usual temps. In that case when it's temporary we can use cooling methods, avoid the heat and not worry about adaptation.

However , if we are trying to get our bodies adapted to the heat because it will be increased long term, such as the start of summer, then this can be a positive adaptive method.

Where this isn't very helpful is if an individual has challenges with nourishment and further reduced intake could put them at further medical risk. This includes such as someone who has the following:

  • an eating disorder or restrictive disordered eating

  • a medical illness causing weight loss

  • medical treatments causing appetite suppression and low intake (such as chemotherapy, depression medications causing low appetite)

What Else Could Cause Low Appetite?

The research also shows that there can also be an impact of body image on food intake. In the summer with people wearing less clothing people are more concerned about how their body looks and this also influences appetite (desire for food) and intake.

What Action Steps Can You Take?

If you would like your body to adapt to the heat, you can still do that slowly using some cooling strategies to reduce body temperatures and increase appetite.

If you are concerned about even a temporary reduced appetite or intake then these cooling strategies become even more important so that you can maintain a typical intake while adapting to the heat. Taking a longer time to adapt to the heat while maintaining a more typical appetite level could be very helpful.

Here are a few tips:

  • Allow graduated exposure to hot environments. During the first few days in a hot environment exposure should be gradually increased with great care to offer opportunities to cool off between exposure. Excessive cooling isn’t advised because this could interfere with heat adaptation. However, remembering a heat wave such as we are experiencing isn’t something we need to adapt to if it's short term.

  • Eat anyways – Appetite does not have to guide your food intake. Eating small regular meals will help to keep your energy levels up all day.

  • Drinking lots of fluids – adequate hydration can help the body cool itself by sweating.

  • Eat nutrient dense foods if you are overall eating less

  • Minimize activity especially during the first few days to week of heat exposure. Activity increases heat in the body which can disrupt appetite further.

  • Use strategies to cool the body down down. Examples include going into a cooler environment in the home, taking a moderately cool shower, spending time in a pool, using a washcloth on the back of your neck. These cooling methods may help to stimulate appetite. Research on food intake in restaurants with AC vs. without show that people order “normally” during a heat wave when sitting inside in AC controlled environments vs. on the patio or in restaurants without AC.

Are Certain Foods Better Than Others?

There appears to be only a small variation in the thermic effect of food depending on the type of food ingested. It is advised to simply eat foods which are appealing to you. There doesn’t seem to be a significant physiological benefit to eating certain temperature or types of food so go with your own personal experience.

Your Dietitian Can Help!

It can be difficult if your appetite and intake is already lower than your target to manage heat waves. Your dietitian on your recovery team is here to help you for these exact challenges. Reach out to your dietitian or to a dietitian specializing in recovery from chronic dieting, disordered eating, eating disorders if you would like support.


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