The development of obesity may be aggravated if obesity itself insulates against heat loss and thus diminishes the amount of food burnt for body temperature control. This would be particularly important under normal animal house conditions where mice experience a chronic cold stress (at 20 °C). We used Scholander plots (energy expenditure plotted versus ambient temperature) to examine the insulation (thermal conductance) of mice, defined as the slope of the Scholander curve at subthermoneutral temperatures. We verified the method by demonstrating that shaved mice possessed only half the insulation of nonshaved mice. We examined a series of obesity models (mice fed high-fat diets and kept at different temperatures, classical diet-induced obesity mice, ob/ob mice and obesity-prone (C57BL/6) versus obesity-resistant (129S) mice). We found that neither acclimation temperature, nor any kind or degree of obesity affected the thermal insulation of the mice, when analyzed at the whole mouse level or as energy expenditure per lean weight. Calculation per body weight erroneously implied increased insulation in obese mice. We conclude that in contrast to what would be expected, obesity of any kind does not increase thermal insulation in mice, and it does therefore not in itself aggravate the development of obesity. It may be discussed to what degree excess adipose tissue has an insulation effect in humans and especially whether significant metabolic effects are associated with insulation in humans.