Shedding the Christmas bulge may not reverse health damage, warn researchers

The annual January battle to lose the Christmas bulge may already be too late to prevent damaging changes to health, a new study suggests.

For the first time, scientists have monitored the inner-workings of the major biological systems of the body as people gained around six lbs over the course of a month.

The team from Stanford University looked at gene function, the metabolism, the expression of proteins, changes to the immune system, populations of bacteria, and the activity of the cardiovascular system.

And they found that the human body undergoes dramatic changes even during short periods of weight gain, some of which are not reversed by weight loss.

Markers of inflammation in the body rose, the immune system began to ramp up and there was a shift in gene activity which is associated with heart failure, in which the body cannot pump blood efficiently to the rest of the body.

"That was quite surprising. I didn't expect 30 days of overeating to change the whole heart pathway," said Dr Michael Snyder, PhD, professor of genetics at Stanford School of Medicine.

"But this all fits with how we think of the human body - it's a whole system, not just a few isolated components, so there are system-wide changes when people gain weight.

"In the end, we literally made billions of measurements."

Previous research has shown that the average Briton gains around two lbs over the Christmas period, although some people studied put on as much as eight lbs, suggesting that festive excess could have long-term health impacts.

Nearly two thirds of Britons are already overweight and one quarter are obese. In 1975 the average Briton had a BMI of 23, which is considered a healthy weight, but today that has risen to an unhealthy 27.

It means that since the 1970s, every person in Briton has roughly gained more than three pounds three lbs (1.5kg) per decade.

11 types of cancer are linked to excess weight which can also lead to Type 2 diabetes, heart disease, stroke and a range of other health problems.

For the new study which was published in the journal Cell Systems, researchers asked 23 participants to embark on a high-calorie diet for a month.

The researchers pooled information from each person's ‘transcriptome’ - molecules which reveal patterns of DNA function, the ‘proteome’, the complete set of proteins an individual actively produces, the 'microbiome' which records the activity of bacteria and the 'genome', the actual DNA code.

Although researchers recorded dramatic shifts, once the participants had dropped the excess weight, their microbes, molecules and gene-expression levels bounced back to their normal levels, for the most part.

However, some shifts in protein and molecule production did persist, even after participants had shed the extra pounds, the study found.

“It is an indication that some of these effects could be longer-lasting," added Dr Snyder.

World Cancer Research Fund’s Senior Science Programme Manager (Research Evidence), Susannah Brown: "This study is important as it helps explain, at the cellular level, how being overweight causes disease. 

"We estimate that around 24,000 cases of cancer in the U.K. could be prevented each year if everyone was a healthy weight.”