“Sitting around at work all day really does give you a bigger bottom,” according to the Daily Mail . The Daily Telegraph ran a similar headline.
While these headlines refer to plump posteriors, they’re based on a laboratory study that found that mouse fat cells produce fat at a faster rate when placed under mechanical stress. This study used fat cells in a laboratory dish, but the mechanical stress the cells were placed under was supposed to mimic the stress that fat tissue is under when people sit or lie down. This stress was applied by growing cells on elastic, which was then stretched.
This study can't really answer whether the pressure from sitting or lying down makes your bottom fat, but its findings support the message that exercise is a key part of a healthy lifestyle.
Further research is needed to clarify whether the mechanical pressure from sitting or lying down for extended periods really does increase bottom fat. In the meantime, people who are concerned about the plumpness of their bottom can make it smaller by eating a healthy diet and doing more exercise.
The study was carried out by researchers from Tel Aviv University and was funded by the Ministry of Science and Technology, Israel and the Ministry of Research, Taiwan and by the Ela Kodesz Institute for Cardiac Physical Sciences and Engineering.
It was published in the peer-reviewed journal American Journal of Physiology – Cell Physiology .
The research was covered accurately by the Daily Mail and the Daily Telegraph , which both also mention other research performed by the authors, on muscle loss in bed-ridden patients.
This was a laboratory-based study. It aimed to determine whether the formation of fat cells – known as adipocytes – is influenced by the weight those cells are placed under, or the “mechanical loading/stresses”.
Other types of cell have already been shown to be sensitive to the mechanical stress they are placed under. For example, bone cells – known as osteoblasts – produce mineralised bone when given sufficient mechanical stimulation.
Although this is an appropriate study design to look at the formation of different cell types, it can’t prove that the mechanical pressure caused by sitting down contributes to bottom fat. For example, the study took place on fat cells in a laboratory, and did not look at fat cells in human bottoms.
In this study the researchers used cells taken from mice and grown in a laboratory.
They started with precursor fat cells, called preadipocytes, which were grown on an elastic layer. Next, they added the hormone insulin in the presence of glucose (sugar) to stimulate those cells to form fat cells – called adipocytes – while stretching the elastic layer. This stretching was supposed to mimic the weight pressure that cells are placed under when people sit or lie down.
The scientists monitored the cells for fat production every two to three days for three to four weeks. They compared that to the fat production of precursor fat cells grown under the same conditions, but without stretching.
The precursor fat cells that were stretched produced fat cells with more and larger fat droplets.
By the time the stretched cells had reached maturity, they had produced up to 50% more fat than the unstretched cells.
The researchers concluded that placing precursor fat cells under mechanical stretching stress causes them to produce fat at a faster rate.
The researchers said this suggests that the weight pressure that we place on fat cells in our bottom when we sit down could contribute to increased bottom fat. They said this means that we may need to take into account the mechanical pressure fat cells are placed under, as well as calories consumed and burned, when thinking about fat production in the body.
In this study, researchers found that mouse precursor fat cells are stimulated to form fat cells that produce fat at a faster rate when they are grown on elastic, which is then stretched. This stretching was supposed to mimic the stress experienced by fat cells when people sit or lie down, although it was applied continuously for three to four weeks.
The scientists said their findings suggest that the weight pressure placed on fat cells in the bottom when we sit down could contribute to increased bottom fat.
The findings support the message that exercise is key to good health, in particular to maintaining a healthy body weight.
But this study has many limitations, as it was performed on mouse cells grown in a laboratory. It’s not clear if the stretching stress that the mouse cells were placed under really is the same or similar to the forces experienced by fat cells in the body when people sit or lie down.
Further research may clarify whether the weight pressure from sitting or lying down does contribute to increased fat in the body. For now, we can all reduce excess fat on our bottoms by eating fewer calories as part of a healthy diet, and by doing more exercise.