One in five Britons is clinically obese
However, the Department of Health has said there is no reason for people who are taking the drug to stop.
Sales of the drug were suspended in Italy last week after reports of health problems, including two fatalities.
Italy's Pharmaceutical Commission decided that the beneficial effects of the drug must be re-evaluated.
Other national agencies have been examining the number of adverse drug reaction reports in preparation for a Europe-wide review by the European Medicines Evaluation Agency.
The Department of Health said that 93 people had suffered a serious adverse reaction after taking the drug.
A spokesman said: "As with all new medicines, the Medicines Control Agency (MCA) and Committee on Safety of Medicines (CSM) are intensively monitoring the safety of sibutramine.
"Patients currently treated with sibutramine (Reductil) can continue to take their medicines as usual.
"However, if they are unwell or concerned they should speak to their doctor."
French reports
Earlier this week French drug regulators reported that they had received 99 reports of side effects, ten of them serious, but no fatalities in patients taking sibutramine.
Abbott Laboratories, which markets the drug, said that 8.6 million people have used sibutramine-based drugs since 1997 and that it was not aware of any substantial change to the drug's risk-benefit profile.
The drug was approved for NHS use by certain groups of patients by the National Institute for Clinical Excellence (NCIE) last October.
It works by suppressing the appetite. It increases the speed at which the body feels full and this encourages weight loss.
Patients who take the drug lose on average 8% of their body weight after two years, and are three times as likely as patients who take a dummy pill to lose 10% of their body weight in the short term.
However, potential side effects include insomnia, constipation and a dry mouth.
Obesity has reached epidemic proportions in the UK with nearly one in five people being classed as obese.