New York, Feb 24 (IANS): Are you one of those busy bees often skipping breakfast? Here's why you should never miss out on the largest meal of the day.

Not eating the first meal of the day could make you inefficient in fighting off infections that can make you prone to a range of diseases from heart disease to cancer, according to a new animal study.

The research, led by a team at the Icahn School of Medicine at Mount Sinai, showed that skipping meals triggers a response in the brain that negatively affects immune cells. It could also lead to a better understanding of how chronic fasting may affect the body long term.

"There is a growing awareness that fasting is healthy, and there is indeed abundant evidence for the benefits of fasting. Our study provides a word of caution as it suggests that there may also be a cost to fasting that carries a health risk," said lead author Filip Swirski, Director of the Cardiovascular Research Institute at Icahn.

The study, published in the journal Immunity, analysed two groups of mice: one group ate breakfast right after waking up, and the other group had no breakfast.

Researchers collected blood samples in both groups when mice woke up, then four hours later, and eight hours later. They found differences in monocytes -- white blood cells that are made in the bone marrow and travel through the body, where they play many critical roles, from fighting infections, to heart disease, to cancer.

After four hours, 90 per cent of monocytes in mice from the fasting group disappeared from the bloodstream, and the number further declined at eight hours. Meanwhile monocytes in the non-fasting group were unaffected.

In fasting mice, researchers discovered the monocytes travelled back to the bone marrow to hibernate, affecting the production of new cells in the bone marrow.

Next, the researchers continued to fast mice for up to 24 hours, and then reintroduced food. The cells hiding in the bone marrow surged back into the bloodstream within a few hours. This surge led to heightened levels of inflammation.

Instead of protecting against infection, these altered monocytes were more inflammatory, making the body less resistant to fighting infection.

Swirski emphasised that while there is also evidence of the metabolic benefits of fasting, this new study is a useful advance in the full understanding of the body's mechanisms.