Ok, not the same source I read it from but this site has these numbers:
A human body produces at least 240 BTU/hour
Basal metabolism = 1 kcal/min * 60 min/hr = 60kcal/hour * 4 BTU/kcal = 240 BTU/hr
A single candle flame produces 850 BTU/hour

So a single candle is more like ~3.5 bodies..

The site also has what looks like formulas that you might be able to use to figure out the inside temp vs outside temp with the BTUs you calculate are heating the area vs the BTUs you calculate you loose.. but I only scaned the whole thing quickly after I found the information so I'm not even sure what its talking about heating in this site...