If you like thematic investing, you've come to the right place. Here are four stock ideas for investors who like to look at the big picture and find ways to profit from hot trends in the economy. The ideas involve GE HealthCare Technologies (GEHC 0.86%), Delta Air Lines (DAL 2.07%), Johnson Controls (JCI 0.90%), and nVent Electric (NVT 1.11%)

Investing on a theme can be lucrative, but you don't want to go all in on trend investing. It's better to treat it as a piece of a well-diversified portfolio. It might be better to start small -- say $1,000 -- and work your way into it. If you like following enduring economic trends, parking a relatively small amount of money in these four stocks and seeing how they perform over the next decade could benefit your overall investment portfolio. Let me explain.

Theranostics, not Theranos

Theranostics combines therapeutics and diagnostics whereby one radioactive tracer can identify and diagnose an affected area -- say, a tumor -- and another can target and treat the tumor precisely. While some might confuse the term theranostics with the now-defunct company Theranos and the controversy surrounding Elizabeth Holmes, the two are not connected in any way.

Theranostics is an emerging field in healthcare, and GE HealthCare Technologies is ideally positioned to benefit from it. The company is one of the leading players in medical imaging equipment and the only imaging company that also manufactures the pharmaceutical diagnostics used in theranostics.

As such, the company has a significant growth opportunity in its high-margin pharmaceutical diagnostics business and selling high-precision imaging equipment. It makes GE HealthCare one of the best stocks to buy in the healthcare sector

The air travel recovery is real

After a couple of years of dealing with temporary government-imposed lockdowns and excessive travel restrictions amid the COVID-19 pandemic, people over the past year or so continue to catch up on experiences they wanted to do but went without. That has been a boon to the travel industry generally. Moreover, Delta's focus on the premium traveler means it's ideally placed to benefit in an industry still suffering somewhat from under-capacity. Simply put, demand exceeds supply, and it's showing up in Delta's numbers: Management recently upgraded its full-year revenue expectations to 17% to 20% growth from a prior estimate of 15% to 20%.

If the recovery continues apace, then Delta's earnings and cash flow will enable it to reduce its debt load over the next few years significantly. Hopefully, the industry can get back to the trend of generating value for investors that it was on in 2019

The commitment to net zero is here to stay

Whether you agree with environmental, social, and governance (ESG) investing or not, the reality is the regulatory environment is increasingly in favor of it, and corporations are committing more and more resources toward it. One of the key considerations of ESG investing is the adoption of net zero emission targets: That is, not increasing greenhouse gases in the atmosphere.

As Johnson Controls CEO George Oliver recently pointed out on an earnings call, "Nearly 40% of global energy emissions come from buildings." As such, making buildings more efficient (using smart technology) and reducing harmful emissions is critical to corporations hitting their net zero goals. That's where Johnson Controls' heating, ventilation, air conditioning (HVAC), and digitally connected software and controls come in. 

In addition, there's a renewed focus on creating healthy, clean buildings (with adequate ventilation) after the pandemic. It all adds up to create an incremental market opportunity of $250 billion for the company to play in over the next decade.

Given the growing clamor over net zero, it's a good bet that spending on retrofitting and upgrading HVAC equipment and the adoption of connected technology will only rise over the next decade. 

An electric car being charged.

Image source: Getty Images.

Electrification of everything 

Suppose you want electric cars, charging networks, renewable energy, smart buildings/infrastructure, industrial automation, data centers, connected buildings, rail travel, and anything else you can think of that needs electricity. In that case, you need to spend on electrical infrastructure, whether it's in transmission and distribution or commercial and industrial settings. 

nVent's exposure to this market comes from its position as a leading provider of connection and protection equipment solutions required to meet regulatory requirements. It's a compelling trend, and the company's management has acquired a reputation for constantly beating expectations and generating value for investors. The stock is a great way to play the trend.