Briton Heidi Hepworth, 44, abandoned husband Andy for 30-year-old Mamadou Jallow - flying out to Gambia to meet him, despite never having been abroad before.
Andy, 44, says his wife started changing her behaviour in March - going to the gym, getting a tan and even tattoos.
She tried looking and acting younger, was splashing out on make-up, buying new clothing and going out more, he told the Daily Mail.
He then noticed she had befriended strangers from Africa and Asia on Facebook and was spending a lot of time on her phone.
In April he found an email from Jallow on his wife’s computer.
She left their home in Sunderland in May with her three youngest children, before flying alone to Gambia last week.
A heartbroken Andy said: “It’s a mid-life crisis. It’s like someone else has taken over her body.”
The couple have six children together and Andy has raised the three children she had from a previous marriage as his own.
Police later found the three youngest children - aged six, nine and 11 - staying legally with their 29-year-old sister.
Heidi said from Gambia that her marriage was over before she left.
She told The Sun: “The marriage had problems. We drifted apart.”
She denied Jallow was just trying to get a British passport.