Frostbite is the freezing of the skin and superficial tissues and could be prevented by covering exposed skin. Hypothermia is a decrease in body temperature that occurs when heat loss exceeds heat production. Three factors affecting hypothermia include the degree of insulation (subcutaneous fat, clothing, wet/dry), energy production (body's metabolism), and environmental conditions (temp., water-vapor pressure, wind).
Besides eating whale blubber to develop a layer of subcutaneous "insulation" around your middle (which might take too long), we could become well insulated by dressing in layers, removing layers to minimize sweating, and by staying dry. If it's a typical Worcester winter day we probably want to start with a long underwear layer which will trap some air around us for insulation and pull moisture away from our skin. Natural fibers (i.e. cotton, wool, silk) can be quite warm and are okay for light activity. For heavier exercise, however, synthetic fibers (i.e. Capilene, polypropylene) absorb less moisture and actually carry water droplets away from the skin. One or more insulating layers such as a wool sweater, Thinsulate, or pile (a soft, polyester fabric hat insulates when wet and is quick drying) may be added if out for an extended time. Then finish with a windproof, and preferably waterproof, shell layer. Some synthetic fabrics which allow perspiration to pass through are Gore-Tex, Thintech, Ultrex, and Super Micrft. Don't forget the extremities: a hat is vital to staying truly warm; gloves, insulating socks, neck "gaiters," and headbands all protect you from the cold.
It is known that just by eating we could increase our metabolism and therefore, increase or maintain our core body temperature when out in the cold for an extended time. For those hiking or cross-country skiing, it is recommended that a 600 kcal snack is eaten every 2 hours, and drink plenty of water. What about those foods and beverages that make us "feel" warm - like hot chocolate, red pepper, and alcohol? They don't actually cause an increase in body temperature, but they do create the sensation of warmth by triggering an expansion of veins under the skin. In the case of alcohol consumption this can be especially dangerous. The vasodilatation causes a net loss of heat from the body, but it may go unnoticed and body core temperature could drop to a dangerous point.
Finally, environmental factors have to be taken into consideration when considering how to prepare ourselves for the great outdoors. It's surprising to know that the outside temperature does not have to be below freezing to cause hypothermia. Other environmental factors, namely wind and water, interact with temperature and may create a dangerous condition by facilitating heat loss.
In other words, if we took a swim in the ocean we would lose heat 25 times faster compared to air in the same temperature. And unlike air, water offers little or no insulation at the skin-water interface, so after we came out of the water and our clothes are now soaking wet, we would be warmer with them off than on - even when outdoors. In addition, if we are planning to bike outdoors we better have an idea of the windchill index (indicates what the "effective" temperature is for any combination of temperature and wind speed) since, for example, cycling at 20 mph into calm air at 0 degrees F has a windchill value of -35 degrees F!! That makes a big difference in how we would dress (oh, and don't forget those hands and fingers - they also need covering up).
It is known that cold-related illnesses may be more serious than heat-related illnesses since in extreme coldness one's breathing and pulse could stop more readily than in extreme heat. So remember to safely enjoy the outdoors during winter, avoid being outdoors in the coldest part of the day, take frequent breaks from the outdoors within the day, dress in layers, and drink large amounts of water to prevent dehydration and lethargy. One of the best parts of going out is coming back indoors - so make sure you enjoy yourself and stay warm!