I often see guests at simchas (celebrations) waste so much food, putting mounds on their plate. We seem to take more than we need. Should we be promoting a more responsible balance between hospitality and waste?

Having worked for several caterers and restaurants I can personally testify to the large amount of excess food "wasted" at many celebrations

This is not a "Jewish" Problem. Rather it's a North American problem.  We are a careless society due to our great bounty of food.

It also makes no sense to be so neurotic so as to expect that we can waste no food at all. Such expectations are unrealistic.  Yet, without a doubt there are many ways to reduce excessive waste

1. Smaller portions, because uneaten portions will waste less. Then  allow the more voracious eaters to get "seconds"

2. Provide leftovers to "soup kitchens".  E.g., In Teaneck, NJ a society called "Sheirit haPLATE" takes extra food to the needy.

3. Invite needy people to the simcha. If seating them in the main hall is logistically difficult, then seat them elsewhere and make the leftovers available to them.

4. Have less lavish parties - at least with regard to the food served.

Note:  while buffets and smorgasbords might seem to waste less, in reality they waste about the same amount.

The concept of waste is subsumed in he mitzvah of "bal Tashchit"

 

Your question is not new. Sumptuary laws, enactments against luxury and ostentation, were issued from the Middle Ages into modern times. In the 1200's Rhenish synagogues limited who could attend banquets. Decrees issued in the 15th century limited the number of guests and certain types of clothing. I know of synagogues that have done away with the use of paper goods in an attempt to minimize the waste they generate. The common concerns across all of these examples include: overuse of limited resources, a desire not to arouse jealousy among neighbors, and a certain level of modesty before the Holy One. Based on those precedents it would seem reasonable to teach both hosts and guests restraint around the ways we celebrate at our modern simchas.

 

A broader ethic, bal tashkhit, lest you destroy, also addresses your concern. The Sages took what seems like a very limited-use verse from the Torah and expanded it into a broad mandate for conservation. “When in your war against a city you have to besiege it a long time in order to capture it, you must not destroy its trees... you may eat of them, but you must not cut them down.” (Deuteronomy 20:19) While it sounds as if it only applies in time of war, the Sages reasoned that if you could not destroy this vital resource in times of high stress, you surely could not do so in more relaxed times. They expanded the prohibition against wantonly destroying things to include not only food, but anything that had value.

 

It is, nonetheless, difficult to tell someone else how to spend their resources, particularly when they are celebrating important family events. Some synagogues do share guidelines for simchas that could address the issues of extravagance and waste. Perhaps our rabbis and teachers could use sermons and classes to share these ethical teachings.

 

One can also use the occasion to support those within the Jewish world who are working for a more sustainable environment. Some locales have organizations that collect prepared but untouched food from events and then deliver it to local food banks and charitable agencies. One such organization is Rock and Wrap It Up (http://www.rockandwrapitup.org/) which works with schools, music venues, hotels and others. Additionally, some institutions encourage their members to enhance their celebration by making donations to Tzedakah (charity). MAZON: A Jewish Response to Hunger suggests a donation equivalent to 3% of the cost of the simcha as a way to honor the Jewish tradition of not eating until you have provided for the poor. One might also support American Jewish World Service or any of a number of other institutions that work to apply these ethical principles to our shared world.