I think that greatly depends on what his biggest insecurity is. For example, his height. Then its a safe bet that man would focus on that. Obviously its difficult to pinpoint exaclty what all men lie about due to the large number of variables involved with each individual.
For the majority of men Ive met, they tell me their interested in having a relationship but after a few months of dating they tell you they are afraid of commitment!??? SMH! They have no clue to what they want or are just to afraid to say I'm just NOT that into you".