The study is a single site parallel randomized controlled study. The study will be assessing the effect of a 10% pre-conceptional weight loss intervention vs a control group among healthy couples where the prospective mother is pregnant and overweight or obese (BMI 27-44.9 kg/m\^2). The couples in intervention group will receive dietitian counseling and participate in physical activity sessions to attain the 10% weight loss. The overall objective is to test whether a comprehensive pre-conceptional parental weight loss intervention effectively reduces the risk of offspring overweight, and adiposity and its complications compared to a control group.

The study is a single site parallel randomized controlled study. The study will be assessing the effect of a pre-conceptional weight loss intervention vs a control group among healthy couples where the prospective mother is pregnant (recruited at gestational age 18-36), overweight or obese (BMI 27-44.9 kg/m\^2), between 18-38 years and planning an additional pregnancy within the following 3 years. The investigators will recruit a total of 140 healthy pregnant couples who will be randomized 1:1 to either intervention or control, stratified according to maternal pre-pregnancy BMI and previous or present diagnosis of gestational diabetes. The couples in intervention group will receive dietary counseling by a dietitian from 3 months post-partum of the 1st child until birth of the 2nd child. The goal is to achieve a healthy lifestyle and a moderate weight loss of 10% according to pre-pregnancy weight during the first year. Hereafter, the couples will be guided in weight maintenance until pregnancy of the second child. During pregnancy the goal is to achieve a healthy weight gain. Couples in intervention group will also participate in physical activity sessions every 2nd week and advised to walk with moderate intensity at least 2-4 times a week for at least half an hour. The overall objective is to test whether a comprehensive pre-conceptional parental weight loss intervention effectively reduces the risk of offspring overweight, and adiposity and its complications compared to a control group. The 1st baby born before intervention is started will be the "index child" and the metabolic and anthropometric parameters of the 1st child will be compared to parameters of the second child to assess the effect of the parent's healthy lifestyle between the two pregnancies. The investigators hypothesize that parental weight loss intervention, initiated before conception, will facilitate lower parental insulin resistance, inflammation, body weight and adiposity, incretin responses and energy expenditure compared to usual care. For the offspring the investigators hypothesize that the intervention will reduce adverse pregnancy outcomes with a short-term reduction in the risk of being born large for gestational age with excessive fat mass and a long-term reduction in the risk of developing overweight or obesity as a consequence of both social (family approach) and biological (epigenetic modifications) pathways.