Sure Obamacare is a give-away to the insurance industry, but its not the biggest national insurers United Health Group (NYSE:UNH) and WellPoint (NYSE:ANTM) that are enjoying reform's big benefit. It's small, regional players like Molina Health (NYSE:MOH)Centene Corp (NYSE:CNC), and Health Net (UNKNOWN:HNT.DL) that focus on Medicaid, not the public exchanges, that are seeing profit soar.

Since investors are likely to be game-planning for reform's second open enrollment this November, let's take a closer look at reform's winners and losers this year.

Source: Centene Corp

Exchanges come up short
Despite more than 7 million new paying members signing up for plans offered through the public exchanges, the Affordable Care Act has been a mixed bag for the nation's biggest insurers.

UnitedHealth took a cautious approach to the exchanges this year, so enrollment hasn't moved the needle for them and even though WellPoint offered plans in 14 states, the company's earnings guidance for this year is tepid (at best) when compared to the small regional insurers.

Big insurers stagnant profit is due to a litany of factors, including the high cost of caring for exchange members (many of whom are older or have pre-existing conditions), spending to establish, market, and refine plans, and Affordable Care Act fees and taxes.

As a result, UnitedHealth is guiding investors to expect its earnings per share this year will be essentially flat versus a year ago at roughly $5.50. 

WellPoint is similarly downplaying reform's benefit from membership growth, guiding for earnings this year of at least $8.60 per share, or roughly 4.8% growth from 2013. .

Those profit projections significantly trail forecasts from the private Medicaid insurers.

Molina expects new Medicaid members will boost its profit from $3.13 last year to between $4 and $4.50 per share this year, which works out to growth of at least 28%.Centene's earnings per share during the first six months of this year has jumped 21% to $1.42 from $1.17 last year. And Health Net exited the second quarter expecting to deliver EPS of $3 this year, up from $2.14 in 2013.

Source: WellPoint

A big difference
Insurers participating on the exchanges had to do a lot more educated guessing than competitors running state Medicaid plans. That's because the ACA mandates that insurers pricing exchange plans can only use a handful of factors when pricing plans, and of that handful only one -- cigarette use -- directly relates to any specific individual's health. As a result, insurers priced plans the best they could based on general assumptions of population health, which weighed on their ability to price in profit in their premiums. Additionally, commercial health insurers are on the hook for the majority of the ACA industry tax, which is calculated based on market share.and totals $8 billion this year.

Private Medicaid insurers, however, had it easier. They had already negotiated payments from states based on the number of people covered and (all things equal) those payments already factored in a profit margin for the companies and their share of the ACA tax. That meant that each additional Medicaid member added due to reform dropped the same amount to the insurer's bottom line as any other existing member.

And another thing
In the past year, Medicaid enrollment grew by more than 7.2 million people to 66 million people and that growth is especially impressive given that only 25 states adopted Medicaid expansion outlined in the ACA heading into 2014.

This year, expansion in additional states including New Hampshire and Pennsylvania, will add even more Medicaid members. Whether those new members will be enough to allow Molina, Centene, and Health Net to continue to put up profit growth that outpaces its larger competitors UnitedHealth and WellPoint is uncertain, but it seems that for now it's private Medicaid insurers that gain the most from reform.

Todd Campbell owns shares of Molina Healthcare. Todd owns E.B. Capital Markets, LLC. E.B. Capital's clients may or may not have positions in the companies mentioned. Todd owns Gundalow Advisors, LLC. Gundalow's clients do not have positions in the companies mentioned. The Motley Fool recommends UnitedHealth Group and WellPoint. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.