Nairobi, Jan. 4 -- January always arrives loudly. After December feasts and late-night parties, many people return to the gym intent on undoing the weight gain with sweat and renewed seriousness. For others, getting fit becomes a New Year's resolution.

Gyms are often packed, with cardio classes spilling over and people queuing for treadmills and dumbbell racks. But there is a less crowded corner of the gym-and a type of weight many people ignore: the kettlebell. It is a round weight with a solid handle that looks a lot like a kettle.

While others scramble for space in cardio classes or fight over barbells and squat racks this January, a kettlebell may be all you need to kick-start your fitness goals.

It may not be the most sought-after...