Just like a house, what makes a person feel warm or cold depends on two things; insulation and the furnace. Obviously, if you have less insulation [fat]you lose heat faster. But even with little insulation you can maintain body temperature by revving up the furnace. The body's furnace is metabolism which is dependent on cellular activity, particularly in the muscles. Exercise helps. Metabolism relies on fuel so keeping warm also depends on supplying adequate fuel to the metabolic engine. I would try eating snacks frequently throughout the day, trail mix works well for this. You want something with some high caloric density so that you can eat a little bit and still get 100 to 200 calories. This might mean you need to change your lunch and dinner habits to keep from gaining excessive fat if this concerns you.
Other factors that affect metabolism include hormonal levels, muscle bulk and fluid balance. If it's a concern have your hormones checked, particularly thyroid. Also you should build muscle with resistance exercise and make sure you're well hydrated.
Another reason why it's important enough is the necessity of caloric intake in maintaining metabolic hormone levels. When a person eats less than 80% of their required daily intake, [taking into account exercise], their metabolic hormone levels drop off significantly.
As for being able to handle heat, this also depends on insulation and fluid balance.
Hope this helps.
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