You can still
lose weight sitting in an office. I did! Buy some hand weights and use them regularly. If you drive to work, park your car further away. If you take public transport, get off one stop earlier. If there are stairs, go up and down them on your coffee break.
Get rid of the chips, go for a pack of nuts instead. They are crunchy, fill you up quicker, lower in fat and are high in protein, all good stuff.
If you drink coffee etc, go for skim milk rather than full cream.