This study is to compare the effects of high fat overfeeding on metabolic risk factors in children born though assisted reproduction technologies (ART) versus children conceived naturally (controls). The investigators will utilize state of the ART measures to characterize the physiological, endocrine and molecular responses to high fat overfeeding.

The investigators hypothesize that children conceived following ART will have greater responses to high fat dietary challenge and that this will be associated with DNA hypermethylation of genes that are involved in lipid metabolism.

This study represents a novel initiative by the investigators to determine whether children conceived through ART have different metabolic responses at baseline or in response to high fat overfeeding as compared to age and body mass index-matched spontaneously conceived controls. Furthermore, the investigators will identify any differences in DNA methylation of candidate genes involved in lipid metabolism in adipose tissue and blood, to determine whether this is related to adverse outcomes during high fat overfeeding. The results from this study will help answer growing questions of the future health of In vitro fertilisation (IVF) babies, and may stimulate further research into optimising protocols for ovarian stimulation or in-vitro conditions during early blastocyst development.

Inclusion Criteria:

• Post-pubertal healthy individuals aged 18-25years

Exclusion Criteria:

• Participants are ineligible if they have any significant medical conditions (e.g. personal history or clinical manifestation of cardiovascular disease, type 2 diabetes),
• strong family histories of diabetes or cardiovascular disease (e.g. first-degree relatives),
• take concomitant medications (eg: metformin),
• if they smoke or drink >140g of alcohol/week, , or
• were born prematurely (<37 weeks), or
• from mothers who had gestational diabetes.